The way you typed out this sentence was a bit confusing but I think you were saying...
For a weekly car rental, a car rental company charges customers a flat fee of $100 + and charges 10 cents for every mile traveled. write an equation for the amount of a weekly rental car that travels 15 miles (Please let me know if I am wrong)
The equation would be
10+10 +10+ 10+ 10+ 10+ 10+ 10+ 10+ 10+ 10+ 10+ 10+ 10+ 10 = 150 cents
so they would be charging $1.50
Hoped this helped!
Have a great day/night! :)