y = mx + b
mx is the slope, with m being the actual slope and x being there to signify that that is the slope. b is the y-intercept.
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y = 4/3x + 8
In this case, 8 is the y-intercept. Plot a point at (0,8).
4/3 is the slope. After you plotted the y-intercept, go up 4 spaces, then go to the right 3 spaces.
Then draw a line connecting the dots.