There is mistake in your question .

it should be x litres of fuel per kilometer

and then x+5 litres of fuel per kilometer.

solution:

Distance traveled before servicing the car = 400 km

fuel consumed per kilometer (in litres)= x

therefore total fuel consumed before servicing of car = 400*x

Distance traveled after servicing the car = 400 km

fuel consumed per kilometer (in litres)= x +5

therefore total fuel consumed after servicing of car = 400*(x+5)

=400x +2000

hence total fuel consumed = 400x + 400x +2000

= 800x +2000

Since the data provided by the question is not sufficient to evaluate the value of x . Hence we get the answer in terms of x.

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