So here's how it is:
The equation given in the OP does not use a fraction slash. It uses a slash. They are two different characters.
The paradigm for regular slash usage in denoting mathematical operations without a math editor is that / denotes division and is interchangeable with ÷. As such, anyone well-versed in arithmetic would be aware that if you were trying to indicate a fraction slash, parenthesis (in the fashion of 6/(2(1+2)) would be needed to avoid confusion.
There's only one set of parenthesis in the OP, thus leaving us to wonder what the intended equation was supposed to be. We were asked to solve, though, so we use Occam's razor to find the answer is 9.
So:
1) this is a troll, and a copypasta
2) if not a troll, the first person to post it was not well-versed in math
3) to reiterate the / is used informally over the internet to signify ÷ (because of laziness, but that's the paradigm). If you deny this, you're a fucking aspie retard.