Answer:
48 miles
Explanation:
What we must do is calculate the car's performance, that is, the number of miles per gallon of gas, like this: 
208/13 = 16 
which means that for each gallon of gas you can travel a total of 16 miles. 
They tell us they have 3 gallons of gasoline left so they can go: 
16 * 3 = 48 
If your goal is 42 miles away, that means you can make it and you still have 6 more miles to go.