18000cm³
So we start off with 18000cm³, and we need to convert it to kg. Since we don't have a direct conversion for cm³ to kg, we have to use two conversions to solve the problem.
1cm³=1g
1000g=1kg
So we take 18000cm³ and convert it to grams and then convert it to kilograms.

Now we just multiply the top and the bottom values by each other...

The cm³ and g cancel out, so we're left with 18kg
Answer=18kg