Answer:
x = 10.5
Explanation:
If you draw a line from the center to either end of 18.8, this will make a right triangle with hypotenuse is x, one side is 4.7, the other side is 18.8/2 = 9.4
so the Pythagorean Theorem states that a^2 + b^2 = c^2
x^2 = 4.7^2 + 9.4^2 = 22.09 + 88.36 = 110.45
x = 10.5