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Math Gym
Subtraction Guide

Subtraction Level 23: 4d - 3d (cascade borrow). borrow-window subtraction.

1. Release thousands

1. Release thousandsRelease one digit; only borrow stays active.
answer strip
6 - 0 = 6; drop 6.

2. Release hundreds

2. Release hundreds
answer strip
Pay right borrow; release 4: 8 - 3 - 1 = 4.

3. Release tens

3. Release tens
answer strip
Borrow 10; pay right borrow: 11 - 5 - 1 = 5.

4. Release ones

4. Release ones
answer strip
Borrow 10; release 5: 12 - 7 = 5.

5. Read answer

5. Read answerDrop finished digits; borrow is gone.
Read 6 | 4 | 5 | 5 as 6455; borrow is gone.