Start by finding the slope.
Pick 2 points on the line and find the “rise” and “run” between them.
To get from (0,3) to (4,0), you’d need to go “down 3” and “right 4”.
Since the slope is “rise over run” and a rise of “down 3” means a rise of “-3”, your slope is -3/4.
Next find the y-intercept: (0,3)
Use the 3 as your b-value for the slope-intercept form.
y=mx+b becomes y= -3/4 x + 3