Ответ:а) (3757 + 939) + 4061 = 4696 + 4061 = 8757.б) (34 271 + 20 001) + 49 999 = 54 272 + 49 999 = 104 271.в) 18 699 + (7701 + 13 800) = 18 699 + 21 501 = 40 200.г) 17 212 + (2788 + 1465) = 17 212 + 4253 = 21 465.