Solution:

None

The sum of numbers from 0-9(0,1,2,3,4,5,6,7,8,9) is 45 and therefore can be divisible by 3 and 9.

Solution:

5 minutes

Solution:

0! or cos(0)

Solution:

18

Solution:

28 =>1+2+4+7+14

cannot be 1 (as number cannot be included)

Solution:

114(37+38+39)

Solution:

3

Solution:

10968

Water image is 89601

Solution:

117(1+3+5,3+4)

Solution:

12345679

12345679 × 9 = 111111111 (only 1s)
12345679 × 18 = 222222222 (only 2s)
12345679 × 27 = 333333333 (only 3s)
12345679 × 36 = 444444444 (only 4s)
12345679 × 45 = 555555555 (only 5s)