How many competitions are there where the  competition type is 'Friendly'?
select count(*) from competition where competition_type = 'Friendly'
Among those results, how many competitions are there for each country?
select country from competition where competition_type = 'Friendly' group by country
What about for type 'Tournament'?
select country from competition where competition_type = 'Tournament' group by country
Which countries held both types of competitions?
select country from competition where competition_type = 'Friendly' intersect select country from competition where competition_type = 'Tournament'