Use subtraction to find the lengths of segments WX and XY.
Point W is on (9,3), point X is on (5,3) and point Y is on (5,9), if I'm reading this correctly.
Point W and point X match with their y-values, so we ignore them. Subtract the x-values, 9 and 5, to get the length. In this case, the length is 4 units.
Point X and point Y match with their x-values, so we ignore them. Subtract the y-values, 3 and 9, to get 6.
Since the problem is asking for length, you always subtract the smaller number from the larger one, as you can't have a negative distance or length.