a) 17 + 54 + 3 = 17 + 3 + 54 = 20 + 54 = 74

b) 29 + 37 + 43 = 29 + 80 = 109

c) 1250 + 186 + 14 = 1250 + 200 = 1450

d) 542 + 79 + 8 + 21 = 542 + 8 + 79 + 21 = 550 + 100