There is no digit that can replace the ? in 2?67 to make it divisible by 4.
All multiples of 4 are even, 2?67 is an odd number and so cannot be a multiple of 4.
0.
Add 6 to it and so 8784/18 = 488
29 is not divisible by 3 and how any digit will alter that depends on how that digit is to interact with 29.
If the number is divisible by 9 the sum of its digits (its digital root) must be divisible by 9. 5+6+8+9 = 28 The next multiple of 9 is 36 and that is 8 more. So the missing digit must be 8.
99996
It depends on whether you mean the highest digit that you add or subtract or multiply by!
6 (or 0)
The 3, to the left.
No single digit determines divisibility by 3.
123456
Any integer divisible by 9 has digits whose sum is divisible by 9. The sum of the digits in 2530 is 2+5+3+0 = 10, and the sum of 1+0 = 1. Having an additional digit "8" in the number, or replacing the "0" with an "8", would make a number divisible by 9. Thus 82,530; 28,530; 25,830; 25,380; 25,308; or 2,538 are all divisible by 9.
6