Đáp án:
$\begin{array}{l}
- 2x + 3 \times \left\{ {12 - 2\left[ {3x - \left( {20 + 2x} \right) - 4x} \right] + 1} \right\} + 45\\
= - 2x + 3\left\{ {12 - 2\left[ {3x - 20 - 2x - 4x} \right] + 1} \right\} + 45\\
= - 2x + 3\left[ {12 - 2\left( { - 3x - 20} \right) + 1} \right] + 45\\
= - 2x + 3\left( {12 + 6x + 40 + 1} \right) + 45\\
= - 2x + 3\left( {6x + 53} \right) + 45\\
= - 2x + 18x + 159 + 45\\
= 16x + 204
\end{array}$
