Subtraction Level 5: Mixed (mastery). borrow-window subtraction. 1. Release tens15 - 91. Release tensRelease one digit; only borrow stays active.15minus91 - 0 - 1 = 0answer stripleading zeroPay right borrow; release 0: 1 - 0 - 1 = 0.2. Release ones2. Release ones15minus915 - 9 = 6answer stripleading zero6Borrow 10; release 6: 15 - 9 = 6.3. Read answer3. Read answerDrop finished digits; borrow is gone.0 | 6 -> 6answer 6Read 0 | 6 as 6; borrow is gone.
