Instead of borrowing from the top number, you add 1 to the next column of the bottom number
It is also called equal additions. Take 73 - 28. The ones need help, so compute 13 - 8 = 5, then instead of crossing out the 7 you add 1 to the bottom tens digit: 7 - 3 = 4. Answer: 45. Adding ten to the top row and one ten to the bottom row cancels out, so the difference stays correct.
