Subtracting Mixed Numbers

Question 1:

2 5 6 - 2 1 8
17 24

Question 2:

4 1 10 - 3 1 3
23 30

Question 3:

5 1 2 - 3 5 8
15 8 = 1 7 8

Question 4:

5 1 9 - 3 7 8
89 72 = 1 17 72