$A$ cricketer whose bowling average is $12.4$ runs per wicket takes $5$ wickets for $26$ runs and thereby decreases his average by $0.4$. The number of wickets taken by him till the last match was:

The average age of students of a class is $15.8 \text{ years}$. The average age of boys in the class is $16.4 \text{ years}$ and that of the girls is $15.4 \text{ years}$. The ratio of the number of boys to the number of girls in the class is:

$A$ number,$x$,equals $80 \%$ of the average of $5, 7, 14$ and a number $y$. If the average of $x$ and $y$ is $26$,then the value of $y$ is:

The average age of $80$ boys in a class is $15.$ The average age of a group of $15$ boys in the class is $16$ and the average age of another $25$ boys in the class is $14.$ What is the average age of the remaining boys in the class?

Of the three numbers,the average of the first and the second is greater than the average of the second and the third by $15$. What is the difference between the first and the third of the three numbers?

Ten years ago,the average age of $P$ and $Q$ was $20 \text{ years}$. The average age of $P, Q,$ and $R$ is $30 \text{ years}$ now. After $10 \text{ years}$,the age of $R$ will be (in $\text{years}$):