2. Order of selections is important and no repeats. P(20,5)
= 1,860,480.
6. 6!/[1!2!1!1!1!] = 360.
10. CP(13) = (13-1)! = 479,001,600.
14. 10x10x10x10x9x9x10x10x5 = 405,000,000.
18. 24x24x24 + 24x24 = 14,400.
22. 2x4x3x12x1 = 288.
26. [Total] - [only evens] - [only odds] = 5x5x5 - 2x2x2 -
3x3x3 = 90.
30. 10!/[3!5!2!] = 2,520.
