David drives 210 miles a week for work. That means the car is used 210miles/week
He fills his petrol tank twice a week. Each fill up is for 42 litres
That means he fill the tank 2x42litre= 84 litres/week.
The mileage should be : (210miles/week)/ (84 litres/week)= 2,5miles/litre
Answer: 2,5miles/litre