1) -13-(-7)+(-7) = -13+7-7 = -13

2) -3+(-8)-(-13) = -3-8+13 = -11+13 = 2

3) 72-(-12)-104 = 72+12-104 = 84-104 = -20

4) -15-(-14)+(-24) = -15+14-24 = -15-10 = -25