913
- 426
487 would be your total but your question is how many times we would have to regroup, so.
First, you would have to borrow from the 1 because 3 is smaller then 6. Second, you would have to borrow from the 9 because you can't take 2 from 0. So there you would have to regroup twice to work this problem.
Hope that helps you. :-)