Combinations from 90 objects, taken 3 at a time is 90C3 = 90*89*88/(3*2*1) = 117,480.
90
You could make 10*10*10*26*26*26 combinations, or 17576000 combinations.
11*3*3 = 99 combinations.
13 combinations of 3
You can make 5 combinations of 1 number, 10 combinations of 2 numbers, 10 combinations of 3 numbers, 5 combinations of 4 numbers, and 1 combinations of 5 number. 31 in all.
36
9.
Just one. The order of the element in a combination does not matter.
Two . . . . . 38 and 83.
3 x 5 = 15
12
18