How to solve:
Problem:
9 5
- 5 7
Bring 10 from the left to the right:

(90 + 5 = 80 + 15)
8 15
9 5
- 5 7
Subtract 15 - 7 in the right column:
8 15
9 5
- 5 7
8
Subtract 8 - 5 in the left column:
8 15
9 5
- 5 7
3 8

Here's one to try:

      





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(Starts timer)
     




              





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