Subtract two numbers column-by-column with borrowing steps shown.
Long subtraction processes each column from right to left. When the top digit is smaller than the bottom digit, borrow 10 from the next column to the left (reducing that column by 1). Continue until all columns are processed.
Subtraction
Difference = Minuend − Subtrahend, column by column with borrowing
When a column's top digit is smaller than the bottom digit, you 'borrow' 10 from the next column to the left — that column's digit decreases by 1, and the current column gets +10.
You cascade the borrow: move left until you find a non-zero digit, reducing it by 1 and turning all the zeros in between into 9s.