| $$ \begin{aligned}\frac{15}{45}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 15 : \color{orangered}{ 15 } }{ 45 : \color{orangered}{ 15 }} \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{1}{3}\end{aligned} $$ | |
| ① | Divide both the top and bottom numbers by $ \color{orangered}{ 15 } $. |