Answer: [tex]8\sqrt{5}[/tex]
Step-by-step explanation:
By the geometric mean theorem,
[tex]\frac{y}{16}=\frac{4}{y}\\\\y^{2}=64\\\\y=8[/tex]
So, by the Pythagorean theorem,
[tex]8^2 + 16^2 = x^2\\\\320=x^2\\\\x=\boxed{8\sqrt{5}}[/tex]
