What's the answer and how did you solve it?

The answer is F. Here's why:

One and two are the exact equation the numbers are just flipped around. For example:

-2 + 3 = 1 or 3 - 2 = 1 

Since only one and two is not answer choice I checked the other two. 

For the fourth one you'd just distribute the -4 so it would look like this:

-4 x 2 = -8 and -4 x -x = 4x

So it would be 4x -8 or -8 + 4x which is the same as the other two.