last digits together are double of first two digits . what is the number ?

lets assume first digit is x, then the 4th digit will be 2x.
also assume 2nd and 3rd digits are y.
then from => last two digits are double of first two digits, we can say
y(2x) = 2*(xy)

We can rewrite is as 10y + 2x = 20x + 2 y
8y = 18x

4y = 9x; => y/x = 9/4
as x and y are integers y => 9, x => 4

thus the car number is 4998