E = A + 7 (1) ("Erica is 7 years older than Allen.") E + 5 = 2(A+5) (2) (" In 5 years . . . From eq(1), substitute the expression for E into eq(2). You will get (A + 7) + 5 = 2*(A+5) A + 12 = 2A + 10 12 - 10 = 2A - a 2 = A Answer. Allen is 2 years old; Erica is 2 + 7 = 9 years old.