Question
Answer
$$a+20-(a-20)=40$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}a+20-(a-20)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}a+20-a+20 \xlongequal{ } \\[1 em] & \xlongequal{ } \cancel{a}+20 -\cancel{a}+20 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}40\end{aligned} $$ | |
| ① | Remove the parentheses by changing the sign of each term within them. $$ - \left( a-20 \right) = -a+20 $$ |
| ② | Combine like terms: $$ \, \color{blue}{ \cancel{a}} \,+ \color{green}{20} \, \color{blue}{ -\cancel{a}} \,+ \color{green}{20} = \color{green}{40} $$ |
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