How many combinations of 3 numbers are there?

Answer 1

6

for example, 123

123

132

321

213

231

312

* * * * *

WRONG.

Those are permutations, not combinations.

There are 8 possible combinations:

123

12

13

23

1

2

3

and finally, the null combination.

Answer 2

999

Answer 3

9

Answer 4

9

Answer 5

905