George's Mistake would be her miscalculation during her 2nd step. Where instead of distributing 2 to (x + 20), she has changed it to -x + 20, when in reality, it should have been 2x + 40.
Answer: The force, F, acting on a charged object varies inversely to the square of its distance, r, from another charged object. When the two objects are 0.64 meter apart, the force acting on them is 8.2 Newtons