RIGHT ANSWERS ONLY PLS <333

90*

Step-by-step explanation:

because a 90 degree rotation is to the right on its side

The independent variable is the number of concert goers which we can call x. The function f(x) represents the total cost of the tickets. We can write: 

f(x) = $21 * x + $5, where the * symbol represents multiplication 

So the total costs are: 

x=1: f(1) = $26 
x=2: f(2) = $47 
x=3: f(3) = $68