Intermediate Algebra, Chapter 2, Review Exercises, Section Review Exercises, Problem 74

Evaluate $ak + bt = 6r$ for $k$


$
\begin{equation}
\begin{aligned}
ak + bt - bt &= 6r - bt
&& \text{Subtract $bt$ from each side}\\
\\
ak &= 6r - bt
&& \text{Evaluate}\\
\\
\frac{ak}{a} &= \frac{6r - bt}{a}
&& \text{Divide each side by } a\\
\\
k &= \frac{6r - bt }{a}
&& \text{Simplify}
\end{aligned}
\end{equation}
$