(1) 6C2 * 4C2 * 2C2 = 15 * 6 = 90
(2) 6C2 * 4C2 * 2C2 / 3!= 90/6 = 15
(3) 6C1 * 5C2 * 3C3 = 6 * 10 * 1 = 60
(4) 6C1 * 5C2 * 3C3 * 3!= 60 * 6 = 360
(5) 3^6 - 6C6 * 3 - (2^6 - 2) * 3 = 540
或者
(6C4 + 6C3 * 3C2 + 6C2 * 4C2 / 3!) * 3!= 540
(6) 6C2 * 5!= 1800
(7) 5C2 = 10