What solution does Benvolio suggest to Romeo in Romeo and Juliet?

Your question is not very specific, so I am going to
assume that the scene you are refering to is Act I scene 2, when Romeo confesses to
Benvolio what is bothering him and how he talks about his love-sick state thanks to his
infatuation with Rosaline. It is this that is causing his aloof attitude and behavioiur.
However, serendipitously (or perhaps not given the outcome), at this moment a servant
comes announcing the ball that is to be held at the Capulet's house that night, and
Benvolio thus proposes his solution to Romeo's melancholy
state:

At
this same ancient feast of Capulet's

Sups the fair Rosaline
whom thou so loves;

With all the admired beauties of
Verona.

Go thither, and with unattainted
eye

Compare her face with some that I shall
show,

And I will make thee think thy swan a
crow.

Thus Benvolio suggests
that they go to the ball, and that there he will point out women who are far more
beautiful than Rosaline, thus curing Romeo of his love-sick state and his infatuation
with her.