Answer:
The length of WZ is 17.5 (which agrees with the third answer in the list)
Explanation:
Notice that we are in the presence of an isosceles triangle where two sides are exactly equal (sides WZ and WX).
The perimeter (additions of all sides) of the triangle is 50, and the size of side XZ is given as 15.
Then if we subtract 15 from 50, we get the addition of the two equal sides: 50 - 15 = 35.
So, now divide this by 2 to get the length of just one of the unknown sides:
35 / 2 = 17.5