Fix typo in isomorphic curves exercise: E_{7,5} instead of E_{5,12}

chapters/elliptic-curves-moonmath.tex

@@ -209,7 +209,7 @@ \subsubsection{Isomorphic affine \concept{short Weierstrass} curves}
 \end{exercise}
 
 \begin{exercise}
-\label{ex:isomorphic_TJJ13} Consider the \curvename{Tiny-jubjub} curve from \examplename{} \ref{TJJ13} and the elliptic curve $E_{5,12}(\F_{13})$ defined as follows:
+\label{ex:isomorphic_TJJ13} Consider the \curvename{Tiny-jubjub} curve from \examplename{} \ref{TJJ13} and the elliptic curve $E_{7,5}(\F_{13})$ defined as follows:
 \begin{equation}
 E_{7,5}(\F_{13}) = \{ (x,y)\in \F_{13}\times \F_{13}\;|\; y^2 = x^3 + 7x +5\}
 \end{equation}