Subtraction Level 4: Mixed 1d/2d - 1d. borrow-window subtraction. 1. Release tens13 - 81. Release tensRelease one digit; only borrow stays active.13minus81 - 0 - 1 = 0answer stripleading zeroPay right borrow; release 0: 1 - 0 - 1 = 0.2. Release ones2. Release ones13minus813 - 8 = 5answer stripleading zero5Borrow 10; release 5: 13 - 8 = 5.3. Read answer3. Read answerDrop finished digits; borrow is gone.0 | 5 -> 5answer 5Read 0 | 5 as 5; borrow is gone.
