The graph below displays gas mileage for a new car.  

1. Use the graph to predict the number of miles the car could travel with three gallons of gas.

   Answer (a):

   A line drawn through the two points would cross $3$ at about $100$ miles, so that is a reasonable estimate.

2. Use the graph to predict the number of miles the car could travel with five gallons of gas.

   Hint (b):

   Where does the line from part (a) cross $5$ gallons?