In how many ways 2 persons can be selected from 4 persons?

From a group of 3 boys B_1, B_2, B_3 and 2 girls G_1, G_2 , 2 are selected at random. In how many ways the 2 persons can be selected from the group

In how many ways 7 persons can be selected from among 5 Indian, 4 British & 2 Chinese, If atleast two are to be selected from each country?

In how many ways 5 persons can be seated in a row ?

In how many ways can 4 persons be selected from amongst 9 persons ? How many times will a particular person be always selected?

In how many ways can a committee be selected from 15 persons if the committee is to have : 3 members.