My friend told me the right answer is 288.
He went trough that discussion, but came up with the idea of testing the problem on machines, since they need to follow a convention (that was his way of thinking).
When I asked him, he was like "obviously it is 288!"
And indeed, even google says it is 288. . ., because u need to see 48/2 as one number, and (3+9) as another (numerator). Or, in other way, multiplication has the same priority as division, so in the case of this problem, u just solve from left to right.
Remembering there's no difference in doing (+) first or (-) first when you have an basic equation, such as a+b-c-d+e (just to say + has no priority over -). What do you think?