| $$ \begin{aligned}3(4v+x+y)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}12v+3x+3y\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{3} $ by $ \left( 4v+x+y\right) $ $$ \color{blue}{3} \cdot \left( 4v+x+y\right) = 12v+3x+3y $$ |