If Edwin got a 95% of the questions right on a 20 question quiz, .95(20) is 19, meaning that he got 19 questions right. 20-19 is 1, which means he got 1 question wrong.
That has a y intercept at y=-1. For every one block to the right we go three blocks up, so that's a slope of 3/1=3. So in slope-intercept form our equation is