Instead of taking away, count forward from the smaller number to the larger and add the jumps.

To find 823 − 398, count up from 398 to 823:

• 398 → 400 is 2
• 400 → 823 is 423
• Total jumps: 2 + 423 = 425.

Check: 823 − 398 = 425. ✓ This is how shopkeepers make change. It shines when the two numbers are close, or when the subtrahend is just under a round number.

5.05 — balance to 15.05 − 10.00.

Add 0.02 to both numbers:

15.03 − 9.98 = 15.05 − 10.00 = 5.05.

This is the cleanest case for balancing: the number being subtracted is just under a round value.