Answer:
30
Explanation:
The midsegment of a triangle (VX) is half the length of the side it's parallel to (YZ).
This is because there are two similar triangles (triangle WYZ and WVX). We know that they are similar triangles as they exhibit side angle side similarity (the ratio between two corresponding sides is the same as the ratio between the other two corresponding sides, i.e. WX/WY = 1/2 and WV/WZ = 1/2; and there is a shared angle between those two sides). Since the ratio of side lengths is 1/2 for the other two sides, it also should be 1/2 for the third side.
VX = 1/2 YZ
Rewrite in terms of t
t - 15 = 1/2 t
Rearrange and solve
1/2 t = 15
t = 30