Your step #2 is incorrect. The result from step #1 is 0999. So step #2 should be 9990 - 0999 = 8991. If you continue on from there, you'll see that it works out.

## Your step #2 is incorrect.

Your step #2 is incorrect. The result from step #1 is 0999. So step #2 should be 9990 - 0999 = 8991. If you continue on from there, you'll see that it works out.