How Does Raoult's Law Apply to Calculating Vapor Pressure in Solutions?

[Qube]

Homework Statement

http://i.minus.com/juL6gvGzvWdm.png

Homework Equations

Raoult's law: Pressure of solution = Mole fraction of solvent multiplied by vapor pressure of pure solvent. We're assuming non-volatile solutes.

The Attempt at a Solution

My solution:

https://scontent-b-mia.xx.fbcdn.net/hphotos-prn1/v/556873_10201073170213135_1235629214_n.jpg?oh=a01e718c3f2218dc3d130fd0007be82b&oe=528964FD

Prof's solution:

http://i.minus.com/jbtmawYMvRpDpX.png

Who's right?

 

[Saitama]

I agree with your answer.

 

[Qube]

Yeah, it seems as if he used the mole fraction of the solute instead of the mole fraction of the solvent, which is a major boo-boo.