Beginning Algebra With Applications, Chapter 2, Review Exercises, Section Review Exercises, Problem 40

Simplify $-3[2x - (7x -9)]$

$
\begin{equation}
\begin{aligned}
&= -3[2x + (-1)(7x) - (-1)(9)] && \text{Use the Distributive Property}\\
\\
&= -3[2x + ((-1) \cdot 7) x + (1)(9)] && \text{Use the Associative Property of Multiplication to group factors}\\
\\
&= -3[2x - 7x + 9] && \text{Simplify}\\
\\
&= -3[-5x + 9] && \text{Combine like terms}\\
\\
&= -3(-5x) + (-3)(9) && \text{Again, by using the Distributive Property}\\
\\
&= ((-3)\cdot(-5)) x - (3)(9) && \text{Use again the Commutative Property of Multiplication}\\
\\
&= 15x - 27 && \text{Simplify}
\end{aligned}
\end{equation}
$