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

$b=\dfrac{2A}{h}$
$\bf{\text{Solution Outline:}}$ To solve the given equation, $A=\dfrac{1}{2}bh$ 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{1}{2}bh \\\\ 2\cdot A=2\cdot\dfrac{1}{2}bh \\\\ 2A=bh \\\\ \dfrac{2A}{h}=\dfrac{bh}{h} \\\\ \dfrac{2A}{h}=b \\\\ b=\dfrac{2A}{h} .\end{array}