Three years ago,the average age of a family of $5$ members was $17$ years. $A$ baby having been born,the average age of the family is the same today. The present age of the baby is (in years):

Eleven years earlier,the average age of a family of $4$ members was $28 \, \text{years}$. Now,the average age of the same family with $6$ members is still the same,even though $2$ children were born in this period. If they belong to the same parents and the age of the first child at the time of the birth of the younger child was the same as the total number of family members just after the birth of the youngest member,then what is the present age of the youngest member of the family in years?

In a coconut grove,$(x+2)$ trees yield $60$ nuts per year,$x$ trees yield $120$ nuts per year,and $(x-2)$ trees yield $180$ nuts per year. If the average yield per year per tree is $100$,find the value of $x$.

The average earning of a mechanic for the first four days of a week is $Rs. 18$ and for the last four days is $Rs. 22$. If he earns $Rs. 20$ on the fourth day,his average earning for the whole week is (in $Rs.$)

The average of six numbers is $20$. If one number is removed,the average becomes $15$. What is the number removed?

$A$ cricketer gives $12.4$ runs per wicket. He gives $26$ runs and takes $5$ wickets in a match,after which his average becomes $12$ runs per wicket. How many wickets had been taken till the last match?