Chapter 1, Equations and Inequalities - 1.5 Use Problem Solving Strategies and Models - 1.5 Exercises - Skill Practice - Page 38: 23

$y=7x-16$

Let the equation have the form $y=mx+d$. $m$ is the rate of change and shows how much $y$ increases by when $x$ increases by $1$. Hence here $m=7$. Then since $y=12$ when $x=4$, $12=4\cdot7+d=28+d\\d=-16$. Thus the equation is: $y=7x-16$