Are the equations m+3= -5 and m= -2 equivalent?

We can apply -2 inside the equation.
m+3=-5
-2+3=-5
This is incorrect because -2+3 is not equal to -5, it is equal to 1. 

Lets find the correct value for m
m+3=-5
    -3  -3
m=-8
So the value that would make our equation true is m=-8
Because
-8+3=5

No because if you substitute m for -2, you'll see that -2 plus 3 equals 1, not 5.