the additions method seem to be taught in two variations, which differ only in psychology. continuing the example of , the first variation attempts to subtract 9 from 6, and then 9 from 16, borrowing a 10 by marking near the digit of the subtrahend in the next column. the second variation attempts to find a digit which, when added to 9, gives 6, and recognizing that is not possible, gives 16, and carrying the 10 of the 16 as a one marking near the same digit as in the first method. the markings are the same; it is just a matter of preference as to how one explains its appearance.