How to subtract integer numbers: calculate the difference and learn to subtract multiple digits numbers, column subtracting method, from right to left

The ones digits line up in the first column from the right.

The tens digits line up in the next column to the left.

And so on...

The borrowing is a two step process:

Subtract 1 from the top digit in the column of the tens: 4 - 1 = 3.
Cross out the top digit you've borrowed 1 from: 4.
Write the answer above that digit: 3.

When borrowing, 1 ten = 10 ones.
Add 10 to the top digit in the column of the ones: 10 + 3 = ¹3.

After borrowing, the subtraction has become:
13 - 9 = 4.
4 is the ones digit.
Write it down at the base of the ones column.

Subtract 1 from the top digit in the column directly to the left.
But that digit is zero. You need to go further left.

Subtract 1 from the nearest column to the left with a non-zero top digit.
That is the column of the thousands: 2 - 1 = 1.
Cross out the top digit you've borrowed 1 from: 2.
Write the answer above that digit: 1.

Cross out the zero(s) that you were going across to the left: 0.
Write a 9 above each one of the crossed out zeros.
Why? In fact we have subtracted 1 from 20: 20 - 1 = 19.

When borrowing, 1 hundred = 10 tens.
Add 10 to the top digit in the column of the tens: 10 + 3 = ¹3.

After borrowing, the subtraction has become:
13 - 5 = 8.
8 is the tens digit.
Write it down at the base of the tens column.

0 9 - 9 = 0.
0 is the hundreds digit.
Write it down at the base of the hundreds column.

2 1 - 1 = 0.
0 is the thousands digit.
Write it down at the base of the thousands column.