1 - 4 / 7 = 3 / 7 ( It means that it is 3 / 7 of the aquarium left to fill with water ) 5 / 6 L ------ 4 / 7 x L --------- 3 / 7 5 / 6 : x = 4/7 : 3/7 5 / 6 : x = 4 : 3 4 x = 3 * 5/6 4 x = 15/6 x = 15/6 : 4 x = 5/2 : 4 = 5/8 L Answer: Jacob needs 5/8 L more to fill the aquarium, or 5/6 + 5/8 = 35/24 L ( in total ).