| $$ \begin{aligned}\frac{12}{30}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 12 : \color{orangered}{ 6 } }{ 30 : \color{orangered}{ 6 }} \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{2}{5}\end{aligned} $$ | |
| ① | Divide both the top and bottom numbers by $ \color{orangered}{ 6 } $. |