If you want to include 0, the overall interval is 115 times 0.01, or 23 times 0.05 or 11.5 times 0.10. The latter might make it harder to plot 1.14, so I'd probably use an interval of 0.05.
Between 6 or 7 and about 25 intervals on a graph's scale are about right. More makes it pretty busy and sometimes difficult to tell which mark is associated with the number. A fewer number is indicated only if there are a fewer number of discrete values that need to be shown to adequately identify the data points.
To isolate b on one side of the equation, all you have to do is subtract mx from both sides, so the answer is
y-mx =b
Do you mind if I re-arrange it slightly before we solve it ?
You said 20x + 3.00y ≥ 500
Subtract 20x
from each side: 3.00 y ≥ -20x + 500
Divide each side by 3 : y ≥ -20/3 x + 500/3
Make it an equation,
and graph this line: y = -20/3 x + 500/3
The line is made out of all points where 'y' is EQUAL to
1/3 of (-20x + 500).
The inequality wants to see all the points that are equal to it
AND all the points that are greater than that.
So the graph of the inequality is the line AND every point that's
anywhere above the line. It's called the "half-infinite plane"
bounded by the line.