Question 1154861
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He charges $40 as a fixed rate for the first hour plus $20 for each additional hour.
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<pre>
TIME,x    COST, y
0          0
1         40
2         40+20
3         40+2*20
4         40+3*20
x         40+20(x-1)
</pre>
<pre>
For x=0                 y=0
For x=1                 y=40
For x more than 1       y=20(x-1)+40
</pre>

The minimum time for cost $140,
{{{20x-20+40=140}}}
{{{20x-20=100}}}
{{{20x=120}}}
{{{x=6}}}--------------six hours of tutoring


The max time if cost $200,
... you can figure this ....