## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$x=6$
Using the properties of equality, the value of $x$ in the given equation, $c\cdot\dfrac{21}{a}=\dfrac{7cx}{2a}$, is \begin{array}{l}\require{cancel} \dfrac{2a}{7c}\cdot\dfrac{21c}{a}=\dfrac{7cx}{2a}\cdot\dfrac{2a}{7c} \\\\ \dfrac{2\cancel{a}}{\cancel{7c}}\cdot\dfrac{\cancel{7c}\cdot3}{\cancel{a}}=\dfrac{14acx}{14ac} \\\\ 6=x \\\\ x=6 .\end{array}