Question

What is the radius of f?

Answer 1

this is a simple right triangle problem.
a^2 + b^2 = c^2

the hypotenuse (or c) is 9 +x
and a is x
And b is 15

So so we sub in the values
x^2 + (15)^2 = (9+x)^2

x^2 + 225 = x^2 + 18x + 81
144 = 18x
8 = x