Just one.
The order of the element in a combination does not matter.
11*3*3 = 99 combinations.
13 combinations of 3
3 x 5 = 15
14 * * * * * Wrong! There are 15. 4 combinations of 1 number, 6 combinations of 2 number, 4 combinations of 3 numbers, and 1 combination of 4 numbers.
137, 173, 317, 371, 713, 731 Six combinations can be made.
9.
36
Two . . . . . 38 and 83.
12
As there are 26 letters in the alphabet. You can calculate the number of combinations by multiplying 26x26x26, giving you the answer 17576.
There are: 35C3 = 6545 combinations
36
4
14 * * * * * Wrong! There are 15. 4 combinations of 1 number, 6 combinations of 2 number, 4 combinations of 3 numbers, and 1 combination of 4 numbers.
137, 173, 317, 371, 713, 731 Six combinations can be made.
Two make combinations you would take 2x1=2 combinations only
233 = 18 combinations.