The first three can be selected in 9c3 ways which equals 84. The second three can be selected in 6c3 ways which equals 20. Then the third set of three can be selected in 3c3 which equals 1 way. Now we want three things to happen, so multiply 84 and 20 and you get 1680. The order of this does not matter so divide 1680 by 3 and you have 280!!
