Your problem statements are a bit incomplete. Share the graphs, please.
The equation –3y = 15 – 4x rewritten in slope-intercept form is:
-3y = -4x + 15, or, after dividing all terms by -3,
y = (4/3)x - 5
The y-intercept is (0, -5), and the slope of the line is 4/3.
the least value out of the data shown is 5, maybe if you post a picture with it i could a little more.