Solution

Explanation:Suppose the vessel initially contains 8 litres of liquid.

Let x litres of this liquid be replaced with water.

Quantity of water in new mixture = (3-3x/8+x)litres.

Quantity of syrup in new mixture = (5-5x/8) litres.

(3-3x/8+x)=(5-5x/8)

=> 5x + 24 = 40 - 5x

=> 10x = 16 => x = 8/5

So, part of the mixture replaced = (85×18) = 1/5.