To find x, we have to use the pythagorean theorem.
a^2 + b^2 = c^2.
In our problem,
a = 3
b = ?
c = 6.5
(3)^2 + b^2 = (6.5)^2
Simplify the left and right side.
9 + b^2 = 42.25.
Subtract 9 from each side
b^2 = 33.25.
Take the square root of each side
b = 5.8.
Multiply 5.8 by two becuase 5.8 is the radius and we are looking for the diameter
x = 11.6