$$ \begin{aligned}-7x-5x& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-12x\end{aligned} $$ | |
① | Combine like terms: $$ \color{blue}{-7x} \color{blue}{-5x} = \color{blue}{-12x} $$ |