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.
The two triangles will be similar (same shape, and each side of one triangle the same multiple of the corresponding side of the other triangle), but not necessarily the same size.
The key word here is "similar;" be sure you understand what that means in trig.
