[AWK]

 A couple daye ago dshipp17 on Undergraduate General Chemistry Forum
presented the following problem:
A sample of an ethanol–water solution has a volume of 54.2 cm³ and a mass of 49.6 g. What is the percentage of ethanol (by mass) in the solution? (Assume that there is no change in volume when the pure compounds are mixed.) The density of ethanol is 0.789 g/cm³ and that of water is 0.998 g/cm³.
This problem literally may be found in many textbooks, sometimes concentration in proof should be calculated.
On the Undergraduate General Chemistry Forum this problem was solved using two different, but equivalent methods (http://www.chemicalforums.com/index.php?)topic=90360.msg323744#msg323744).
But it may be solved using other set of equations from which two of them were already used (basic variable may be also percentages, or mixed).
Find other possible solutions.

[bubblegumpi]

Could you use vapour pressure to figure this out?