I don't understand math; that's why I'm here. I thought that I was doing pemdas exactly...addition comes before subtraction. It seems to me that I'm doing exactly what they gave me.

No. As explained in (

this) lesson, addition and subtraction are at the same "level" and are done at the same time, from left to right. There is no "distribution", even were addition to come "first" in some manner, which it does not. The "plus" signs in front of the final three terms do not become "minus" signs simply because a prior term had a "minus" sign; they retain their additive aspect.

You may wish to review number properties (

here) -- specifically, the commutative property of addition -- to understand why "-1,600 + 100,000 + 150,000 + 1,500" is the same as "100,000 + 150,000 + 1,500 - 1,600", and is never equal to -100,000 - 150,000 - 1,500 - 1,600.

If you have further questions, please be specific. Thank you.