Chevy Silverado
1) In this question, we are going to find the unit rate so that we can get the best relation: mileage/gas
2) Let's start with the 2007 Ford F-150:

So that Ford F-150 makes 1.6 miles per gallon
b) Chevy Silverado:

Thus, the Chevy Silverado makes 17 miles per gallon.
c) Toyota Tundra:

3) Thus the best gas mileage is: Chevy Silverado