You drive an average of 450 miles per week in a car that gets 22 miles per gallon. with gasoline priced at $3.50 per gallon on average, approximately how much would you save each year on gas if you instead had a car that got 40 miles per gallon?

First we have to compute how much we spend money each year. 
Compute like this:
is the number of gallons consumed each week. 
In one year there is 48 weeks. 
Then  is the number of gallons a year. 
Now compute the price: 

We do the same process with a car consuming 40 miles per gallon. 
tex] \frac{450}{40}=11.25 [/tex] gallon consumed per week. 
   gallons consumed per year. 
is the amount paid each year in gallons. 
So we are saving the following amount: