please solve this puzzle.

[ravijoshi offline]

I've made 200 puzzles and this is the hardest of them. please try to solve it if you can.
THIS IS AN CHALLENGE

6 6 6
8 7 4
5 6 ?
what number should come at '?' and why.

[TROLOLO offline]

3

[crays offline]

eine 9:D

[corneliuscornpunchy offline]

Yo man. Its 7

[ravi offline]

Oh! friends it looks like I've forgotten to tell you that you all have to post answer with a logic.
9, 3 and 7 are not correct answers of this puzzle and a hint! :- The answer is not in "Z" set (The number is a fraction).

[thunderbeast offline]

its either 2 or a variable seeing hat the answer is not given but a question mark has taken its place the question mark is (in this case) A variable so it can be any number therefore if 2 is incorrect the answer is pi because pi ( just like pie lol ) is an infinite term it is many numbers at once. -
I am studying to be a math matician in college and my professor siad that he has seen this sort of puzzle before so hahah I win wheres my money. > <
U

[ravijoshi99 offline]

"[quote="thunderbeast"]its either 2 or a variable seeing hat the answer is not given but a question mark has taken its place the question mark is (in this case) A variable so it can be any number ..."
You are wrong. I have put this puzzle online, so, I know the answer and the answer is not longer than 1 decimal place. So, You can't say that answer is "Pi" or something like that. Answer is a number x, 0 < X < 7. X≠pi. 0 < 4 < X <7