The ratio of the present ages of $R$ and $S$ is $11:17$. $11$ years ago,the ratio of their ages was $11:20$. What is $R$'s present age (in years)?

The respective ratio between the speeds of a car,a jeep,and a tractor is $3:5:2$. The speed of the jeep is $250\%$ of the speed of the tractor,which covers $360 \text{ km}$ in $12 \text{ hours}$. What is the average speed of the car and the jeep together in $\text{km/h}$?

Three numbers $A, B$ and $C$ are in the ratio of $12: 15: 25$. If the sum of these numbers is $312$,find the ratio between the difference of $B$ and $A$ and the difference of $C$ and $B$.

There is a ratio of $5:4$ between two numbers. If $40\%$ of the first number is $12$,then $50\%$ of the second number is:

In an army selection process,the ratio of selected to unselected candidates was $5:1$. If $100$ fewer candidates had applied and $20$ fewer had been selected,the ratio of selected to unselected candidates would have been $6:1$. How many candidates had applied for the process?

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?