Intermediate Algebra for College Students (7th Edition)

To subtract two real numbers $a$ and $b$, change the operation to subtraction and then change the sign of the subtrahend to its opposite. In symbols, $a-b = a + (-b)$. (refer to the step-by-step part for an example)
To subtract two real numbers $a$ and $b$, change the operation to subtraction and then change the sign of the subtrahend to its opposite. In symbols, $a-b = a + (-b)$ Example: $9-3 = 9+(-3) = 6$