Teaching Subtraction through Strategy! . The Think Ten strategy for subtraction works in a very similar way to the Think Ten strategy for addition where a ten is added instead of a number close to ten. Subtracting ten instead of a number close to ten (usually 9 or 😎 can make a basic fact that is not yet known automatically easier to work out by using place value understandings. . The subtraction basic facts are the subtraction inverses of the addition basic facts (0 0 to 9 9). So the largest to