а) 24a + 16 + 13a = (24a + 13a) + 16 = 37a + 16
Ответ: 37a + 16
б) 25 ⋅ a ⋅ 16 = (25 ⋅ 16) ⋅ a = 400 ⋅ a = 400a
Ответ: 400a