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

$b=3A-a-c$
$\bf{\text{Solution Outline:}}$ To solve the given equation, $A=\dfrac{a+b+c}{3}$ for $b ,$ use the properties of equality to isolate the variable. $\bf{\text{Solution Details:}}$ Using the properties of equality to isolate the variable, the equation above is equivalent to \begin{array}{l}\require{cancel} A=\dfrac{a+b+c}{3} \\\\ 3\cdot A=3\cdot \dfrac{a+b+c}{3} \\\\ 3A=a+b+c \\\\ 3A-a-c=b \\\\ b=3A-a-c .\end{array}