Chapter 3 - Equations and Problem Solving - Chapter 3 Review Problem Set - Page 137: 27

$m=\dfrac{y-b}{x}$

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}