Hi!
Let's find the volume of the fish tank. To do that we need to
multiply the length times the width times the height.
18 x 12 x 10 = 2160Now find the volume of the water, by
changing the height value from 10, to 6, because the height of the water is 6 inches.
18 x 12 x 6 = 1296
Simplify the fraction
The answer is

Hope this helps! :)
-Peredhel