Question

if jacob used 1/7 of a liter of water to fill 1/9 of a fish aquarium how many liters are needed to fill the aquarium

Answer 1

1/9 of the aquarium was filled with 1/7 liter

1 whole fraction  of the aquarium will be filled =    1/7 ÷ 1/9

                                                        = 1/7 * 9/1  = 9/7

   9/7 liters or 1   2/7 liters will be needed.