jmc

The area of a right triangle can be found by using the legs of triangle as the base and height. In the three isosceles triangles, the length of their second leg is the same as the side that is connected to the $3-4-5$ triangle. $$\begin{array}{rl}W& =(3)(4)/2=6\\ X& =(3)(3)/2=4.5\\ Y& =(4)(4)/2=8\\ Z& =(5)(5)/2=12.5\end{array}$$ Plugging into the answer choices, the only that works is $\boxed{X+Y=Z}$.