a) 85 + 310 = 8050 + 1550 = 9550 = 1910
b) 23 + 34 + 16 = 812 + 912 + 212 = 1912
c) 56 - 29 = 4554 - 1254 = 3354
d) 2110 - 34 - 25 = 2110 - 34 - 25 = 4220 - 1520 - 820 = 1920