In a problem/solution essay you want to make sure you clearly identify the problem early in the essay. You would want to do this in the first paragraph. There are several ways to do this. You could start off with statistics about binge drinking, or a particularly good quotation. One very effective way to start off an essay like this is to relate an anecdote. An anecdote is a brief story that communicates the idea. I would think you could find a little story that tells about some sort of binge-drinking-related tragedy that has occurred lately on a college campus.
You also want to make sure that you give an opposing point of view. Something along the lines of “some people feel that binge-drinking is just a rite of passage for college students.” Then refute that opposing point of view with whatever method you did not use in your introduction (stats, quote, anecdote). It’s important to show that you are aware that some people will disagree with you and that you can prove them wrong.
A good way to end is with a “call-to-action” conclusion. With this kind of conclusion you suggest a course of action that can be taken to combat the problem.