Subtraction Basic Fact: Think Ten 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 8) 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 larg