Answer
$x=\dfrac{a+b}{c}$
Work Step by Step
Multiply both sides by $x$.
$x\left ( \dfrac{a}{x} + \dfrac{b}{x}\right )=x\cdot c$
Use distributive property.
$x\left ( \dfrac{a}{x} \right )+ x\left ( \dfrac{b}{x}\right )=xc$
Cancel common factors.
$a+ b=xc$
Divide both sides by $c$.
$\dfrac{a+b}{c}=\dfrac{xc}{c}$
Simplify.
$\dfrac{a+b}{c}=x$
