Simple,
so you have...
-5m=-35
You are trying to find m, so, to isolate the variable divide both sides by -5:
[tex] \frac{-5m}{-5} = \frac{-35}{-5} [/tex]
m=7
Now, to check your work, plug in m.
-5(7)=-35
-35=-35
Thus, you know your answer is correct.