Question
Solve: 21 – 3 (x – 7) = x + 20
✓
Answer
$\begin{aligned} & 21-3(x-7)=x+20 \\ & \Rightarrow 21-3 x+21=x+20 \\ & \Rightarrow 42-3 x=x+20 \\ & \Rightarrow 42-20=x+3 x \\ & \Rightarrow 4 x=22 \\ & \Rightarrow x=\frac{22}{4}=\frac{11}{2}=5 \frac{1}{2} \\ & \therefore x=5 \frac{1}{2}\end{aligned}$
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