Question

5 teams 1-5, play each team once. How do you figure it?

Answer 1

Figure what?
Do you want the total number of games?
That would be C(5,2)
= 5!/(3!2!)
= ....

You could actually just list them, since the count is quite small.
If you had A,B,C,D, and E
matches would be
AB AC AD AE
BC BD ....
....