Jacob used 1/7 of a liter of water.
He needs to fill 1/9 of the fish aquarium.
Find how many liters would Jacob need to fill the aquarium
=> Let x = liters of water need to fill the aquarium
=> x/1 = 1/7 divided by 1/9
=> x = 1/7 x 9/1
=> x = 9/7, since this is an improper fraction, let’s convert it to mixed fraction
=> x = 1 and 2/7
So, Jacob need 1 and 2/7 liter of water to fill the whole aquarium.