Answer: 17
Step-by-step explanation: To find the radius of Q, you'd have to solve for x. So, 4x+3=7x-6, which results in x equaling 3. Next, bisect the chord EF, so it will be 8. Solve for QA, which is 15 and use the pythagorean theorem to solve: x^2=15^2+8^2 -> x=17