diff --git a/ast.py b/ast.py
index d76ed29..ed81d2f 100644
--- a/ast.py
+++ b/ast.py
@@ -24,7 +24,7 @@ def _fixed(self, node):
                 del node.matched[i]
 
         # This flattens rules with a single matched rule.
-        if len(node.matched) is 1 and isinstance(node.matched[0], RuleMatch) and node.name not in ('mbd', 'mrw'):  # The last condition fixes small matrices like [1], [1,2], and [1|2].
+        if len(node.matched) is 1 and isinstance(node.matched[0], RuleMatch) and node.name not in ('mbd', 'mrw', 'opb'):  # The last condition fixes small matrices like [1], [1,2], and [1|2].
             return self._fixed(node.matched[0])
 
         # This makes left-associative operations left-associative.
@@ -39,19 +39,13 @@ def _fixed(self, node):
         if node.name == 'mui':
             return self._fixed(RuleMatch('mul', [node.matched[0], Token('MUL', '*'), node.matched[1]]))
 
-        # This flattens matrix rows into parent matrix rows.
-        if node.name == 'mrw':
-            for i in range(len(node.matched) - 1, -1, -1):
-                if node.matched[i].name == 'mrw':
-                    node.matched[i:] = node.matched[i].matched
-                    return self._fixed(node)
-
-        # This flattens matrix bodies into parent matrix bodies.
-        if node.name == 'mbd':
-            for i in range(len(node.matched) - 1, -1, -1):
-                if node.matched[i].name == 'mbd':
-                    node.matched[i:] = node.matched[i].matched
-                    return self._fixed(node)
+        # This flattens nested nodes into their parents if their parents are of the same type.
+        for tpe in ('mrw', 'mbd', 'opb'):
+            if node.name == tpe:
+                for i in range(len(node.matched) - 1, -1, -1):
+                    if node.matched[i].name == tpe:
+                        node.matched[i:] = node.matched[i].matched
+                        return self._fixed(node)
 
         if isinstance(node, RuleMatch):
             for i in range(len(node.matched)):
diff --git a/common.py b/common.py
index 7509805..79371b9 100644
--- a/common.py
+++ b/common.py
@@ -45,6 +45,7 @@ def _str(self, node, depth=0) -> str:
     (r'identity',           'OPR'),
     (r'trnsform',           'OPR'),
     (r'rref',               'OPR'),
+    (r'solve',              'OPR'),
     (r'[a-zA-Z_]+',         'IDT'),
     (r'=',                  'EQL'),
     (r'\+',                 'ADD'),
@@ -67,7 +68,7 @@ def _str(self, node, depth=0) -> str:
 
 class ImmutableIndexedDict:
     def __init__(self, data):
-        self._keys = tuple(item[0].lstrip('^') for item in data)
+        self._keys = tuple(item[0] for item in data if not item[0].startswith('^'))
         self._data = {key.lstrip('^'): values for key, values in data}
 
         # Caching indices cuts down on runtime.
@@ -100,7 +101,8 @@ def key_at(self, i):
     ('mui', ('pow mul',)),
     ('mul', ('pow MUL mul',)),
     ('pow', ('opr POW pow',)),
-    ('opr', ('OPR LPA add RPA',)),
+    ('opr', ('OPR LPA opb RPA',)),
+    ('^opb', ('add CMA opb', 'add')),
     ('neg', ('ADD num', 'ADD opr')),
     ('var', ('IDT',)),
     ('num', ('NUM', 'LPA add RPA')),
diff --git a/rules.py b/rules.py
index 6476ad7..704af4d 100644
--- a/rules.py
+++ b/rules.py
@@ -4,7 +4,19 @@
 from typing import List
 
 from common import Token
-from vartypes import VariableValue, NumberValue, MatrixRowValue, MatrixValue, Value
+from vartypes import VariableValue, NumberValue, MatrixRowValue, MatrixValue, Value, OperatorBodyValue
+
+
+def flatten(l):
+    lst = []
+
+    for elem in l:
+        if isinstance(elem, list):
+            lst.append(elem[0])
+        else:
+            lst.append(elem)
+
+    return lst
 
 
 def var(_, tokens: List[Token]) -> VariableValue:
@@ -23,6 +35,10 @@ def mbd(values: List[Value], _) -> MatrixValue:
     return MatrixValue(values)
 
 
+def opb(values: List[Value], _) -> OperatorBodyValue:
+    return OperatorBodyValue(values)
+
+
 def add(operands: List[Value], operator: Token) -> Value:
     return {'+': operands[0].add, '-': operands[0].sub}[operator.value](*operands[1:])
 
@@ -36,7 +52,8 @@ def pow(operands: List[Value], _) -> Value:
 
 
 def opr(operands: List[Value], operator: Token) -> Value:
-    return getattr(operands[0], operator.value)(*operands[1:])
+    args = operands[0].value
+    return getattr(args[0], operator.value)(*args[1:])
 
 
 def neg(operands: List[Value], operator: Token) -> Value:
@@ -49,6 +66,7 @@ def neg(operands: List[Value], operator: Token) -> Value:
     'num': num,
     'mrw': mrw,
     'mbd': mbd,
+    'opb': opb,
 }
 
 # The mapping for all other rules.
diff --git a/vartypes.py b/vartypes.py
index 38d0c4e..07c77f6 100644
--- a/vartypes.py
+++ b/vartypes.py
@@ -36,11 +36,10 @@ def div(self, other):
 
     def mod(self, other):
         raise EvaluationException('Operation not defined for ' + self.type)
-
     
     def pow(self, other):
         raise EvaluationException('Operation not defined for ' + self.type)
-    
+
     def sqrt(self):
         raise EvaluationException('Operation not defined for ' + self.type)
 
@@ -50,6 +49,9 @@ def exp(self):
     def identity(self):
         raise EvaluationException('Operation not defined for ' + self.type)
 
+    def solve(self, other):
+        raise EvaluationException('Operation not defined for ' + self.type)
+
 
 class VariableValue(Value):
     def __init__(self, data):
@@ -224,6 +226,9 @@ def rref(self):
     def trnsform(self):
         return MatrixValue(self._rref()[1])
 
+    def solve(self, other):
+        return NumberValue(2)
+
 
 class MatrixRowValue(Value):
     def __init__(self, data):
@@ -234,3 +239,10 @@ def __init__(self, data):
 
         else:
             self.value = data
+
+
+class OperatorBodyValue(Value):
+    def __init__(self, args):
+        super().__init__()
+
+        self.value = args
\ No newline at end of file