| $$ \begin{aligned}5x(3xy-2)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}15x^2y-10x\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{5x} $ by $ \left( 3xy-2\right) $ $$ \color{blue}{5x} \cdot \left( 3xy-2\right) = 15x^2y-10x $$ |