In ΔABC, if m∠ A = m∠C, m∠ B= ß (where ß is an acute angle), and BC = x, which expression gives the length of b, the side opposite ∠B?

Barrett is comparing the membership fees for two museums.the art museum charges a one-time fee of $8.25 plus $2.25 per month. the science museum charges a one-time fee of $10.75 plus $3.50 per month. how much does barrett save by joining the art museum instead of the science museum?