#### Answer

-3

#### Work Step by Step

We begin by following the instructions to plug -4 in for a and 7 in for b. Thus, we obtain:
$-7-(-4) $
A key rule to remember is that subtracting a negative is the same as addition. Thus, it follows:
$-7-(-4)=-7+4$
We must recall that a negative becomes more positive when a positive number is added to it. Therefore, we find:
$-7+4=-3$