Question

Find y using Pythagorean theorem or proportion

Answer 1

We have three similar triangles, let's see if we can get this right, right vertex first, then other vertex from small side:

EDF ~ GDE ~ GEF

As ratios that means

ED:DF:EF = GD:DE:GE = GE:EF:GF

x:20:y = 5:x:GE = GE:y:15

Since we're after y we choose

20/y = y/15

20(15) = y²

y² = 300

y = 10√3

y ≈ 17.32