An aquarium weighs 22.5 lb when empty the aquarium is 30 in long 14 in wide and is filled with water to a depth of 18 in. water weighs 0.036 pounds per cubic inch. how much does the aquarium weigh when it's full of water

To get the weight of the aquarium we first calculate the volume of the aquarium.
Volume=(length*width*height)
V=30×14×18
V=7560 in³

But
weight of water is such that for every cubic inches, the weight is 0.036 lb
thus the weight of water will be:
0.036×7560=272.16 lb
Thus the total weight of the aquarium is:
272.16+22.5
=294.66 lb