Update README.md

Signed-off-by: Fabiana 🚀  Campanari <113218619+FabianaCampanari@users.noreply.github.com>

Author: FabianaCampanari

README.md

@@ -771,15 +771,15 @@ Z = 4x_1 + 3x_2
 
 ### ➢ [**Subject to:**]():
 
-$
+$$
 \begin{cases}
 x_1 + 3x_2 \leq 7 \\
 2x_1 + 2x_2 \leq 8 \\
 x_1 + x_2 \leq 3 \\
 x_2 \leq 2 \\
 x_1 \geq 0, \quad x_2 \geq 0
 \end{cases}
-$
+$$
 
 ```latex
 \begin{cases}