Negatives are tricky at first.

However, I found it helps to look at it this way: A negative number and a number with a minus sign in front of it are the same thing. There's no difference.

Also, two negatives cancel out. (x - (-x) = x+x. -x*-x = x*x. etc.)

That tends to help quite a bit.

As for the last one, it's been a while since I had to solve one of these, so I've forgotten exactly what you have to do, and I know that I didn't give you quite enough info to solve it. I'm reasonably certain, however, that you know enough to solve the 2nd one.

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"Science is the poetry of reality." ~ Richard Dawkins