A vessel contains a mixture of two milk M and N is the ratio 7 : 5. When 9 ltr of mixture are drawn off and the vessel is filled with B, the ratio of Mand N becomes 7 : 9. How many ltrof liquid M was contained by the can initially?  Options:
A) 20ltr B) 21ltr C) 23ltr D) 24ltr E) 25ltr
Suppose the can initially contains 7x and 5x of mixtures A and B respectively.   Quantity of M in mixture left = 7x -	7	x 9 ltr= 7x -	21 ltr.   12	4   Quantity of N in mixture left = 5x -	5	x 9 ltr = 5x -	15 ltr.   12	4   7x -	21   4   =	7   5x -	15 + 9   4   9   28x - 21	=	7   20x + 21	9   252x - 189 28  - 21= 
<gadget id="calculator">28  - 21</gadget>
<output>7</output>
7   20x + 21	9   252x - 189= 140x + 147   112x = 336   x = 3.   So, the can contained 21ltr of M   21ltr
<result>B</result>
A vessel contains a mixture of two milk M and N is the ratio 7 : 5. When 9 ltr of mixture are drawn off and the vessel is filled with B, the ratio of Mand N becomes 7 : 9. How many ltrof liquid M was contained by the can initially?