Ron works at the local bookstore for an hour every day. He earns $5 daily from this job. If he adds this amount to his daily allowance, he has $70 at the end of each week. The amount of money Ron receives each week is represented by the equation 7(x + 5) = 70, where x is the amount of Ron's daily allowance. Plug the numbers from the set {5, 10, 15, 20} into the equation to find x, the amount of Ron's daily allowance.