Question: This math problem has got me stumped: The car-rental agency charges $30/day for a car, or $190 for the first week for a rental that lasts an entire week or longer. Jennie rented a car for 11 days. How much, in dollars, did she pay for the rental?
Can you show me the way?
Answer: 
The first 7 days were $190.
There were 11-7=4 days left.
The additional 4 days were 4*30=120.
And 190+120=310.