You can choose the first letter any of 5 ways and for each of those 5 ways to choose the first letter that leaves 4 ways to choose the second letter, so there are 5*4 or 20 ways. They are 1. PE 2. PA 3. PC 4. PH 5. EP 6. EA 7. EC 8. EH 9. AP 10. AE 11. AC 12. AH 13. CP 14. CE 15. CA 16. CH 17. HP 18. HE 19. HA 20. HC Edwin