A2A.The ratio is 5:7.Assume that the vessel contains 120 liters.Water=50 litersSyrup=70 litersSince all the liquid taken out of the vessel is replaced by water, the total volume remains constant.Therefore, we need to ensure there's 60 litres of water and Syrup individually.Therefore, we need to take out 10 litres of syrup and replace it with water.For every 12 litres taken out of the vessel, we replace 7 litres of syrup with water.Therefore, we need to replace (12*10)/7 of the solution with water. (17.142%)Hope this helps.