The price of the car was 18,000. To calculate tax, you turn the percentage into a decimal and multiply it by the price. To find it, you divide the percentage and price.
In this case, you just simply divide 1080 by 6% (0.06), which gives you 18000.
If you multiply 18000 by 0.06, you will get the same thing. Therefore, 18,000 was the price of the car before tax.