Present ages of $X$ and $Y$ are in the ratio $5: 6$ respectively. Seven years hence,this ratio will become $6: 7$ respectively. What is $X$'s present age in years?

What will be the duplicate ratio of $2: 7$?

The ratio between the present ages of Indira and Lizzy is $3:8$,respectively. After $8 \text{ yr}$,Indira's age will be $20 \text{ yr}$. What was Lizzy's age $5 \text{ yr}$ ago (in $\text{yr}$)?

If Rs. $872$ is divided into three parts,proportional to $\frac{1}{2}: \frac{2}{3}: \frac{3}{4},$ then the first part is

In a mixture of petrol and kerosene,the quantity of petrol is $99 \text{ litres}$. If this same quantity of petrol were present in another mixture of petrol and kerosene where the total volume is $198 \text{ litres}$ less than the actual mixture,the concentration of petrol in the actual mixture would be $13.33 \%$ less than that of the new mixture. What is the concentration (in $\%$) of petrol in the actual mixture?

$A$ mixture of milk and water is kept in two separate containers. The ratio of milk to water in one container is $5:1$ and in the other container is $7:2$. In what ratio should the mixtures from these two containers be mixed so that the quantity of milk in the new mixture becomes $80\%$?