1. The problem statement, all variables and given/known data Benzene and toluene combine to form an ideal solution. At 80 C, vapor pressure of pure benzene is 800 mmHg and the vapor pressure of pure toluene is 300 mmHg. If the vapor pressure of the solution is 400 mmHg, what are the mole fractions of benzene and toluene? (A) 60% benzene and 40% toluene (B) 50% benzene and 50% toluene (C) 40% benzene and 60% touene (D) 20% benzene and 80% toluene 2. Relevant equations Pv=xaPa + xbPb 3. The attempt at a solution I could easily back solve by trying each one out. D is correct. (0.2)(800) + (0.8)(300) = 400 but I really wanted to try this problem using the equation above. Instead of backsolving, is there an accurate way to put this formula to use? Thanks in advance.