Think of this problem in terms of a number line:

-9 | | | | -4 | | | 0 | | | | 5

You either start at 5 and move 9 steps backwards, or, start at -9 and move 5 steps forwards.

Either way, you end up at 4.

Backwards motion is to the left, occuring with negative numbers, where forwards motion is moving to the right, occuring with positive numbers.