Expert: Richard J. Raridon - 1/28/2008

Question
I am a Math major and I tutor in Math while I am in school. I am currently
tutoring someone who is doing very basic algebra, maybe even pre-algebra.
She is doing well with it, but she does not know how to write an equation
given a certain amount of data. I have tried to explain it to her, but I don't feel
like I'm getting through. How would you explain it?

Ex: Greta rents out bikes for $4 per hour. Unlike in the previous example,
however, she charges an up-front fee of $8. Fill out the table and write an
equation expressing the cost at any number of hours. (Paraphrased because I
don't remember the exact wording, but you get the idea)

Hour - Cost
0            $8
1            $12
2            
3            
4

She had difficulty with this problem even when the cost was only $4 per hour,
with no initial fee. Can you help me explain it?

Thank you!

Answer
C(ost) = 8 +4H where H is the no. of hours

You should have been able to explain that it's a linear relationship so that results in a straight line.  The standard equation for a straight line is y = mx +b where m is the slope.  Obviously, here,
m = 4 so if you put in y=12 when x=1, you get y = 4x +8