If there is more to the answer than what I give please ask for more!
With

we can find

by substituting 4 into the main function.
So it would look like this:

Hope this helps!
Answer:
Vertical Line test
Step-by-step explanation:
If you can put a vertical line anywhere on the graph, and it doesn't touch more than one point, then it's a function. A function means there are no repeated x values.
Answer:
c=4
Step-by-step explanation:
-5c - 15 = -35
Add 15 to each side
-5c - 15+15 = -35+15
-5c = -20
Divide each side by -5
-5c/-5 = -20/-5
c = 4
Awnser is: T(total)=30(admission)+4(price of rides)x(number of rides)