help to write a join query

Hi my friends
I have to do a query in oracle 11g

but i really dont have any idea.would you please help me?

i want to cumpute the percentage of believers of every religion from the world's population

country:name,code,population

example data "Argentina" "ar" "39144753"


religion:country,name,percentage
example data
ar Jewish 2
ar Protestant 2
ar Roman Catholic 92



oracle 11g, os ubuntu 12.4


thank u in advance