| $$ \begin{aligned}9(-2wt\cdot6)+9w& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}9-12tw+9w \xlongequal{ } \\[1 em] & \xlongequal{ }-108tw+9w\end{aligned} $$ | |
| ① | $$ 2 w t \cdot 6 = 12 t w $$ |