| $$ \begin{aligned}\frac{360}{630}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 360 : \color{orangered}{ 90 } }{ 630 : \color{orangered}{ 90 }} \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{4}{7}\end{aligned} $$ | |
| ① | Divide both the top and bottom numbers by $ \color{orangered}{ 90 } $. |