The scale factor means that figure WXYZ has sides that are 1/3 as long the corresponding sides of figure STUV.
Thus:
WX = (1/3)(117) = 39 mm
WZ = (1/3)(153) = 51 mm
Hmm...looks like your question needs a little more information for you to figure out YZ. Does it it say what kind of shape these are? If so, use the characteristics of that shape to keep working through to the answer.