a)
1. 42.203 - 17.123 = 25.080
2. 123.458 + 29.387 = 152.845
3. 152.845 - 25.080 = 127.765
= 127.765
b)
802.724 - 514.914 = 287.810
287.810 + 15.875 = 303.685
= 304.685
c)
1. 5.158 + 15.234 = 20.392
2. 3.210 + 589 = 3.799
3. 20.392 - 3.799 = 16.593
4. 23.145 + 16.593 = 39.738
= 39.738