You have the system of 2 equations a + b = 14 (1) 70a + 55b = 905 (2) From equation (1), express b = 14-a and substitute it into equation (2), replacing b there 70a + 55(14-a) = 905. From this equation a == 9. ANSWER. 9 printing press of the type A and the rest, (14-9) = 5 printing press of the type B. CHECK. 70*9 + 55*5 = 905 books. ! Correct !