Old question, a FB meme, seen also on G+.
I believe the question originated from the fact that if you use different calculators, you get different answers
This has to do with a convention on some Casio calculators (it's written in the manual, see page E-30, Order of operations), that juxtaposition (called abbreviated multiplication in the manual) takes precedence over division.
So on a Casio the expression
$$6 / 2 (2 + 1)$$
is parsed as
$$6/(2 \cdot (2 + 1)) = 6/6 = 1$$
But if you type
$$6 / 2 * (2 + 1)$$
instead on a Casio, you will get $9$ as a result, as this is parsed as
$$(6/2) \cdot ( 2 + 1 )$$
PS I have now seen the previous post mentioned by @MJD in a comment. So this confirms my suspicion about the origin of the problem, but I do not think any of the answers to the other question mentioned this difference between multiplication and abbreviated multiplication.