15

obviously its Eishu as the answer the teacher made was correcting the chemistry papers because it was the first day the student got murdered and also it cannot be possible that on first day itself tests will be conducted..

cloud

i think it must be  x or y
because in  A NA A SA A A …. A gets increased by one more A in every sequence (i.e., A  then AA and by AAA)
and also it starts with N in first sequence and then by S (i.e., by going four more alphabets in the alphabetical order) and so the letter must be x (i.e., same by going through four more alphabets in the alphabetical order). And it can also be possible that as A is increasing in descending order, forthcoming letter can also go through by five more alphabets in the alphabetical order i.e., y.

4100
4*1000+40+30+20+10

white house is in the middle of all the three

9 as the question ask for the count only for left and not remaining

12+11=123
i.e.,12-11=1 which is the first digit and 12+11=23, the second digit

same 7.5 mins as the time would not change if the quantum of the egg increases

19