What's is the use of encapsulation in transport layer of OSI​

Idon understand these and need some ! ?

Ihave been given the number of guns per 100, and the total firearm-related deaths per 100,000. i have to find the actual number of guns per country and actual number of gun-related deaths. if somebody could show me how to do 1 question, i can finish the rest, i am just confused. tia

Which task uses a simple parameter?