## Elementary Algebra

$m=\dfrac{y-b}{x}$
Using the properties of equality, in terms of $m,$ the given equation, $y=mx+b ,$ is equivalent to \begin{array}{l}\require{cancel} y-b=mx \\\\ \dfrac{y-b}{x}=\dfrac{mx}{x} \\\\ m=\dfrac{y-b}{x} .\end{array}