Explanation:
SADMEP
-10 = -10 +7m
+10 +10
0 = 7m
divide by 7 on both sides
0/7 = 0
m = 0
basically if one side has subtraction you want to do addition to the other. If one side has addition you want to subtract the other. if one side has division you want to multiply, if one side has multiplication you want to divide. if you have and exponent you want to do the root of it (it could a sqaure root, cube root, etc.)
keep in mind you are doing this for both sides since you are trying to cancel out everything else to get to what m equals (or any other variable).
I hope this helps