Question

8=8p+13-3p

Answer 1

8=8p+13-3p
8-13=8p-3p
-5=5p
p=-5/5
p=-1

Answer 2

move all the p terms to one side and constants to the other so we get
8-13 = 8p-3p
evaluate lhs and rhs
-5 = 5p
divide both sides by 5
p = -1