Answer:
f(x) = 5x - 30
Yes it is a function
Step-by-step explanation:
Because when you input 0 you get -30 we know it starts at 0 or (0,-30). This gives us b in the equation y = mx + b.
We know that for every 4 cars washed it increases by 20. So 20/4 is 5. This tells us m = 5.
Plug it all in and you get y = 5x - 30 or f(x) = 5x - 30
