First, let's put all of the variables together.
4m + 5m + 5 + 40 = 180.
Add them.
M is the same multiplier, so we can add 4 and 5 together to make 9m.
Add 5 and 40.
9m + 45 = 180.
From here, we can go two ways. I will show the first way, which is my personal  preference.
We want to get rid of the coefficient on m to isolate it, so we must divide it by its coefficient. The coefficient on m is 9. So, divide m by 9. We must also divide everything else by 9.
9m/9 = 1m
45/9 = 5
180/9 = 20
Plug it in--
m + 5 = 20.
Subtract the 5 from both sides to isolate m.
m = 15.
