Hi myself2014,
First off, since this appears to be a college class assignment, asking someone in this Forum to solve it for you seems like academic fraud.
With that in mind, this question is poorly worded and I believe that it has at least one typo in it.
Here are the concerns:
1) The phrase "13 took rice and plantain"; does this mean that some of these 13 also took beans?
2) The phrase "28 took rice or plantain, but not beans"; does this mean that some of these 28 too BOTH rice AND plantains?
I have a solution that utilizes all of the facts, and assumes that:
1) Some of the 13 people mentioned above also took beans
2) Some of the 28 took rice AND plantains
But my solution involves 55 people and does not account for however many took "none of the meals"; so I think the "40 person total" also seems problematic. It's possible that whoever wrote this question mistyped it.
GMAT assassins aren't born, they're made,
Rich