Question 75386
This is a straight-line relationship and you can find several
points on the line and then find the equation for the line.
Let C = number of riders per day
Let F = fare charged per rider
Here are some points:
C = 800
F = 2.25
---------
C = 760
F = 2.50
---------
C = 720
F = 2.75
---------
C = 680
F = 3.00
---------
C = 640
F = 3.25
---------
Now to find the equation. The slope is the change in the vertical over the 
change in the horizontal. Let's plot C on the vertical and F on the
horizontal. Find m = (change in C)/(change in F) for ANY 2 points
{{{m = (720 - 680) / (2.75 - 3)}}}
{{{m = 40 / -.25}}}
{{{m = -160}}}
Now use the formula that goes
{{{m = (y - y[1]) / (x - x[1])}}} except y is C and x is F.
{{{-160 = (C - 720) / (F - 2.75)}}}
{{{-160F + 440 = C - 720}}}
{{{C = -160F + 1160}}}
This what to plot.
(a) The slope is -160
{{{ graph( 600, 400, -1, 10, -50, 1300, -160x + 1160) }}}
(b)If you make F = 0 in the equation C = 1160
You can see this from the graph, too
(c) If you make C = 0, F = 1160 / 160, F = 7.25
So, at a fare of $7.25, no one will ride.