In a row of $21$ girls, when Monika was shifted by four places towards the right, she became $12^{th}$ from the left end. What was her earlier position from the right end of the row (in $^{th}$)?

If Atul finds that he is twelfth from the right in a line of boys and fourth from the left, how many boys should be added to the line such that there are $28$ boys in the line?

Among $B, F, J, K$ and $W$ each having a different weight, $F$ is heavier than only $J.$ $B$ is heavier than $F$ and $W$ but not as heavy as $K.$ Who is the third heaviest among them?

There are $20$ people working in an office. The first group of $5$ works between $8:00 \,A.M.$ and $2:00 \,P.M.$ The second group of $10$ works between $10:00 \,A.M.$ and $4:00 \,P.M.$ And the third group of $5$ works between $12$ noon and $6:00 \,P.M.$ There are $3$ computers in the office which all the employees frequently use. During which of the following hours are the computers likely to be used most?

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

In the series,$6, 4, 1, 2, 2, 8, 7, 4, 2, 1, 6, 3, 8, 6, 2, 1, 7, 1, 4, 1, 3, 2, 8, 6$,how many pairs of alternate numbers have a difference of $2$?