I first looked up how many gallons in 1 cubic yard.
1 cu. yd. = 201.974026 gal.
That would mean that 18 cu. yd. would be 18(201.974026 gal) = 3635.532468 gal.
The total cost was $300.
Divide $300 by the number of gallons to get $.0825 per gallon.
Now, just multiply the other values times this amount to find your other container costs.