HI Jennifer,

I'm going to evaluate a similar expression,

372 - 136 - (- 251) + (-37).

I would first remove the parentheses. + (- 37) = -37 and -(- 251) = 251 so removing the parentheses gives

327 - 136 + 251 - 37.

At this point I would collect the positive terms collect the negative terms to get

327 + 251 - 136 - 37.

Now add the positive terms and add the negative terms to get

623 - 173.

Finally perform the subtraction.

623 - 173 = 450.

Now try your problems,
Penny