Suppose that W and X are points on the number line. If WX=9 and W lies at 12, where would X be located? If there is more than one location, separate them with commas.
Imagine a number line, and W and X are points on it. The question says WX is 9, meaning that is the distance between them. So, it says that W is at 12. Then, x is 9 units away from 12. So, x can be either 21 (that is 12+9) or 3 (that is 12-9).