Chapter 1 - Solving Linear Equations - 1.3 - Solving Equations with Variables on Both Sides - Monitoring Progress - Page 21: 6

$k=-0.5$

$$\begin{align*} 10k+7+10k&=-3-10k+10k &\text{Add $10k$ to both sides.}\\ 20k+7&=-3&\text{Simplify.}\\ 20k+7-7&=-3-7 &\text{Subtract $7$ from each side.}\\ 20k&=-10 &\text{Simplify.}\\ \frac{20k}{20}&=\frac{-10}{20}&\text{Divide $20$ to both sides.}\\ k&=-0.5 &\text{Simplify.} \end{align*}$$