Question

The company charges $45 a day for the car

as well as charging a one-time $25 fee for
the car’s navigation system (GPS). Write an
equation for the cost in dollars, C, as a
function of the number of days, d, the car
was rented.

Answer 1

I personally find it easier to put my equation in words before actually writing the equation, so for this particular situation, the equation would sound like this :

→ The cost (C) is equal to 45$ a day (d) plus 25$!

Now that your equation is put into words, all that you have to do is write down the equation without the words :

→ C = (45d) + 25

If you want to make sure that your equation is correct, you can try it out, say for instance you want to rent a car for a week, so for a total of 7 days, and you want to see how much it would cost :

d = 7 (in this particular situation)

C = (45 × 7) +25

↓

C = 315 + 25

↓

C = 340

→ So it would cost 340$ to rent a car for a week!

credit goes to naomi479xx for solving this answer.