$A$ can contain a mixture of two liquids $A$ and $B$ in the ratio $7: 5$. When $9 L$ of mixture is drain off and the can is filled with $B$, the ratio of $A$ and $B$ becomes $7: 9$. How many litres of liquid $A$ was contained by the can initially?

Two vessels $\mathrm{A}$ and $\mathrm{B}$ contain milk and water mixed in the ratio $8:5$ and $5:2$, respectively. The ratio in which these two mixtures be mixed to get a new mixture containing $69\frac{3}{13}\%$ milk is

A mixture of milk and water is such that the quantity $3$ of milk is $5$ that of water. The proportion of milk in the mixture is: