5(m+1)=7(m-1)

$$\begin{array}{rll}
5(m+1)&=&7(m-1)\\
5m+5&=&7m-7\\
5m+5-5&=&7m-7-5\\
5m&=&7m-12\\
5m-7m&=&7m-12-7m\\
-2m&=&-12\\
\frac{-2m}{-2}&=&\frac{-12}{-2}\\
m&=&6\\
\end{array}$$

5m+5=7m-7=6 6 is the answer