| $$ \begin{aligned}(7+3)x^3& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10x^3\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{7} + \color{blue}{3} = \color{blue}{10} $$ |