How do I calculate the distance a car can travel based on a fixed fuel consumption rate (in kilometres per litre), the amount of fuel in the tank and the distance already travelled?

Assume that the tank is empty and we add some fuel at the start.

For example, a car has a fixed fuel consumption rate of 6 k/l and I add 3 litres of fuel and I’ve already travelled I don’t know, lets say, 5km.
How do I calculate the quantity of fuel left in the car then after adding the fuel and then travelling over x amount of distance.

Sound travels at 1100 feet per second. What distance could it conceivably travel before it finally loses it energy? Is it dependent on how much energy is produced in conjunction with that sound?

If you travel at a constant speed and the distance you travel varies directly with your travel timeSuppose in 1.5 hours you can walk 5 miles What is the costant of variation and how did you find this?