Subtract Two-Digit Numbers With Borrowing

Subtract 28 from 63. The ones column (3 - 8) requires borrowing 1 ten from the tens column, turning 3 into 13 before subtracting.

Example

sub-63-28.math

   63
-  28
-----

step: ones: 3 < 8, borrow from tens
step: borrow: tens 6 -> 5, ones 3 -> 13
step: ones: 13 - 8 = 5, write 5
step: tens: 5 - 2 = 3, write 3
step: 63 - 28 = 35

borrowing When a digit in the minuend is too small to subtract from, borrow 1 from the column to its left. The left column decreases by 1 and the current column increases by 10, making subtraction possible.