in the additions method, a 10 is borrowed to make the 6 into 16, in preparation for the subtraction of 9, just as in the borrowing method. however, the 10 is not taken by reducing the minuend, rather one augments the subtrahend. effectively, the problem is transformed into . typically a crutch of a small one is marked just below the subtrahend digit as a reminder. then the operations proceed: 9 from 16 is 7; and 40 (that is, ) from 80 is 40, or 47 as the result.