4333 - 3334 = 999 is correct but need to keep 4 digits so write 0999 then you get: 9990-0999=8991 and so on.

## you need to keep it 4 digits

4333 - 3334 = 999 is correct but need to keep 4 digits so write 0999

then you get:

9990-0999=8991 and so on.