geometric mean thing
4x/16=16/x since the 2 triangles are similar
times both sides by 16x
4x²=256
divide both sides by 4
x²=64
sqrt both sides
x=8
ok, so onter one
a²+b²=c²
(4x)²+16²=y²
(4*8)²+256=y²
(32)²+256=y²
1024+256=y²
1280=y²
sqrt both sides
√1280=y
answer is A