Find the number of ways of 9 people can be divided into two groups of 6 people and 3 people.

my working is there are 6! arrangement for 6 people and 3! arrangment for 3 people. then the group of 3 people can be placed at right or left only . so that the 6 people form another group will not be seperated. so my working = 3! x 6! x2 = 8640..

the ans given is only 84