The variables given are the fixed cos (called the flat fee) which is a known variable, that is 75. You also have the variable cost which can change as the mileage increases and that is 0.55 per mile driven.
If the total cost at 1 mile is given as
75.55 = flat fee + fee per mile driven, then the equation would be as follows;
[tex]C=y+\text{0}.55x[/tex]Where C is the total cost, y is the flat fee (which does not change) and x is the number of miles driven. This can now be properly expressed as
[tex]C=75+0.55x[/tex]That is the answer to part (a)
(b) The total cost of renting and driving the truck for 60 miles can now be calculated as follows;
[tex]\begin{gathered} C=75+0.55x \\ \text{Where x equals 60, the equation becomes} \\ C=75+0.55(60) \\ C=75+33 \\ C=108 \end{gathered}[/tex]The cost therefore of renting and driving the truck for 60 miles is $108
