Math/Brain Teaser Help

Okay, so I have two questions. First one:

Insert parenthesis in the following equations to make them true, prove your answers.
Example: Given; 21+13-17=35, you would insert parenthesis so it looks like this; 21+1(3-1)7=35.
Here's the one I can't solve:
32-13+21=-5

Secondly, I can't solve this brain teaser either.
Use four 7's as your only digits, and any math symbols you want, to write a math sentence that simplifies to 18.

Please help me! Thanks!

For the second, 77/7 + 7
I haven't gotten the first yet.

Edit: For the first,
(3)(2) - 13 + (2)1
= 6 - 13 + 2
= -7 + 2
= -5

first is 3(2-13)+21=-5

second (77/7)+7

I can answer the teaser the answer is
77/7+7=18