Explanation:
are you sure the fuel consumption is given by 6,8 km/l ?
normally it is given by l/100km.
but ok, let's assume this is correct.
it would mean the car can drive 6,8 km with every liter of fuel in the tank.
how many liters will the car need to go 450 km ?
well, as many liters as 6,8 fits into 450 :
450/6,8 = 66.17647059... liters
this is not a very fuel efficient car ...