In this problem, you are just being asked the distance between the numbers on the number line.
Example:
X=5, A= - 5
Count the spaces in between the 2 numbers... 5 is on the positive side, any number on the right of a number line is a positive number, and any number on the left of a number line is a negative.
so if you count down from positive 5 to 0, you have jest then moved 5 spaces backwards... now move back 5 again into the negative side, now you should have moved a total of 10 spaces coming from positive to negative.