2×C(n，2)=90

Then, C(n, 2)=45.

The above formula represents the combination number of 2 in n.

Obviously, n= 10.

Therefore, a * * * has 10 teams.

The second question,

One person infects N people, so after two rounds, one person infects n×n people.

That is, n×n=64

So, n=8.

That is, one person infects eight people.