| $$ \begin{aligned}21+2i+13+8i& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10i+34\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{21} + \color{red}{2i} + \color{blue}{13} + \color{red}{8i} = \color{red}{10i} + \color{blue}{34} $$ |