Exam

I don't want to upset anyone but I have to make 3 problems for one of my exams.
I don't know how to work in Ubuntu and I really need to take this exam.

First problem:

Write a script that reads N elements of a vector and then calculates the sum of vector and their average.

Second problem:

To find all users' personal files, accessed in the last 7 days, the minimum size of 5MB. Display format will be:

File [filename] size [dim] KB
directory [path]
-> Has been accessed [nameOfDay] [DayNumber] [NameMonth] [Year] at [hh][mm][ss] AM /PM

And the third problem:

If you get to a computer that runs Ubuntu, and find an open session, find out fast whick user name has left open session, at which time he logged into the system and how much time has passed since then?

Thank you for your help!