I believe you just collect your like terms
1) -2p+4 - because (7p) and (-9p) = (-2p) think of it as 7-9 = -2 // and -1+5 = 4
2) 12h-14 - because (5h) and (7h) = (12h), 5+7 =12 /// -6-8 = -14, think of it was negative 6, then taking away 8 more
3) 7 - because (8b) and (-8b) = 0, and 6 + 1 = 7
4) 5 - because (9a) and (-7a) and (-2a) = 0, because 9-7-2 = 0, and you are left with +5
Keep the variables together when adding or subtracting, ex. 7p+3p-4......7p and 3p are together because they have alike variables, -4 is by itself because it is "different". I apologize if I answered a question wrong or did not help you in understanding the questions, I have not done math in forever.