A can contains a mixture of two liquids A and B in the ratio 7 5 When 9 litres of mixture are d...........

Explanation:

Suppose the can initially contains 7x and 5x litres of mixtures A and B respectively

Quantity of A in mixture left =(7x−7/12×9)=(7x−21/4) litres.

Quantity of B in mixture left =  (5x−5/12×9)=(5x−15/4) litres.

(7x−21/4) /(5x−15/4)+9 = 7/9

⇒28x−21 /20x+21 = 7/9

⇒x=3

 So, the can contained 21 litres of A.

Hence, option 3 is the correct answer.