Abhishek ranks thirteenth in a class of thirty-one students. What is his rank from the last (in $19^{th}$)?

In a row of $35$ children,$M$ is $15^{th}$ from the right end and there are $10$ children between $M$ and $R.$ What is $R$'s position from the left end of the row?

How many $7$'s are there in the following series which are preceded by $6$ but not preceded by $8$ (i.e.,the sequence $6, 7$ where $6$ is not immediately preceded by $8$)?
Series: $8, 7, 6, 7, 8, 6, 7, 5, 6, 7, 9, 7, 6, 1, 6, 7, 7, 6, 8, 8, 6, 9, 7, 6, 8, 7$

$M$ is older than $R$. $Q$ is younger than $R$ and $N$. $N$ is not as old as $M$. Who among $M, N, R$,and $Q$ is the oldest?

In a row of girls, if Savitha who is tenth from the left and Anita who is ninth from the right interchange their places, Savitha becomes fifteenth from the left. How many girls are there in the row?

In the following list of numerals,how many $2$'s are followed by $1$'s but not preceded by $4$?