$A$ cricketer,whose bowling average was $12.4$ runs/wicket,takes $5$ wickets for $22$ runs in a match,thereby decreasing his average by $0.4$. The number of wickets taken by him before this match was:

The average weight of $3$ men $A, B$ and $C$ is $84 \, kg$. Another man $D$ joins the group and the average now becomes $80 \, kg$. If another man $E$,whose weight is $3 \, kg$ more than that of $D$,replaces $A$,then the average weight of $B, C, D$ and $E$ becomes $79 \, kg$. The weight of $A$ is (in $kg$)

$19$ persons went to a hotel for a combined dinner party. $13$ of them spent $Rs. 79$ each on their dinner and the rest spent $Rs. 4$ more than the average expenditure of all the $19$ persons. What was the total money spent by them?

Ashish has earned an average of $4200$ dollars for the first eleven months of the year. If he justifies his staying on in the $US$ on the basis of his ability to earn at least $5000$ dollars per month for the entire year,how much should he earn (in dollars) in the last month to achieve his required average for the whole year?

The average age of $x$ and $y$ is $20$ years. If $z$ were to replace $x$,the average would be $19$ and if $z$ were to replace $y$,the average would be $21$. Find the ages of $x, y$ and $z$.

The average of $6$ numbers is $8$. What is the $7^{th}$ number so that the average becomes $10$?