How do you calculate how tall a child will be

Iam so stuck. what is the worked out answer for this question?

Ben bowled 124 and 188 in his first two games. what must he bowl in his third game to have an average of at least 160?

Florence price's brownies and more sells all types of cookies and pastries. on tuesdays, they markdown all brownies 75% to a sale of $1.50 a dozen. find the selling price and the markdown of a dozen brownies.