Since a serving is 1/2 cup and he needs 72 servings you can multiply 72 by 1/2 and find out that he needs to make 36 cups of punch. Two cups is a pint so he needs (36 / 2) 18 pints of juice. He already has the 8 pints of pineapple juice so 18 - 8 leaves 10 pints of orange juice.
I think its zero. i may be wrong
OK.......
Evaluating [(21 + 6) - 32] 2 * 9

Your answer would be
-90
H0P3 It H3LPS :)
Usually its easier to subtract numbers written vertically because of the sheer fact that you're just taking away instead of adding on. If you have basic idea about adding then you should understand subtracting easier. But, because most schools teach adding first its easier for some.