(x + 10)(y - 5) = 600 ------ eq (ii) ------- Substituting for x in eq (ii) ------- Multiplying by LCD, y (y - 20)(y + 15) = 0 y - 20 = 0 OR y + 15 = 0 y = 20 OR y = - 15 ------- Substituting 20 for y in eq (i) x = 30 ------- Substituting - 15 for y in eq (i) x = - 40