| $$ \begin{aligned}10i+8i& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}18i\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{10i} + \color{blue}{8i} = \color{blue}{18i} $$ |