Answer
$-3b-21$
Work Step by Step
The distributive property allows us to distribute anything multiplied by something inside of the parenthesis to whatever is inside of the parenthesis. Thus, we distribute the negative 3 to everything inside the parenthesis, giving us an answer of $-3b-21$.
(A key rule to remember is that subtracting a negative is the same as addition, so
b-(-7) is the same as b+7).
