Since it asks for function notation, I'll relate the variables accordingly. So, x, the independent variable, is the one that is being adjusted. That would be the amount of miles that he is assigned so x = miles assigned. Next, the dependent variable, f(x), is the amount of cash he is paid, so f(x) = total amount paid.
Here is the function that can be used to represent the situation:
f(x) = 3.50x + 75
Now, plug in 30 to find out how much he earns after completing a 30 mile route:
f(30) = 3.50(30) + 75
f(30) = 105 + 75
f(30) = 180
Also, the $75 is a fixed amount. No variable association.
