Geometry math question no guessing and show work

If two triangles are similar, the corresponding sides are in the same proportion.

Since the L-y-80 triangle is flipped with respect to the 20-x-60 triangle, the couples of corresponding sides are twe following:

- The correspondant side of y is x

- The correspondant side of 80 is 20

- The correspondant side of L is 60

And as we said before, all correspondant sides are in the same ratio. So, we have

Since 80/20 = 4, we can deduce