Answer
B: -3
Work Step by Step
$-b-a\longrightarrow$ substitute the given values for each variable
$=-7-(-4)\longrightarrow$ change subtraction to addition be reversing the sign of the following term
$=-7+4\longrightarrow$ when adding a negative term to a positive term, subtract the absolute values; the sign of the sum is negative since the negative addend has the greater absolute value.
$=-(|-7|-|4|)\longrightarrow$ simplify absolute values
$=-(7-4)\longrightarrow$ subtract
$=-3$
