The add on in a linear equation and t-shirt problem

TMWYK:
-Extra part
-Add or subtract
-Happens w/ head start/up front price
-When linear graphs don't start at the same place

***Where it hits or intersects the y-axis (ex. 45 in headstart) it starts at 0. Add on is 0.


Walkathon T-shirt problem

Given these equations, what do you think the C and n could stand for? Could you make up a problem? 

Mighty T

C= 49 + n
C=cost
n=# of students 
49 to create a design (add on)


No-Shrink T

C=4.5n
C=cost
n=number of students 
No add on, hits 0 axis


R/L 63
Here is the dilemma. I have $120. Which place should I go to buy the maximum amount of t-shirts. 

-Need two ways to justify your thinking