Find mass from mole frac and solution mass

[jesuslovesu]

1. 75g sample of a gaseous mixture contains .51 mole fraction propane. The remainder is butane. What are the masses of propane and butane?



2. X = mol A / mol total

The Attempt at a Solution

P = mol propane
B = mol butane
I tried doing .49P + .49B = X mol propane and .51P + .51B = Y mol butane however that doesn't seem to be solvable. I'm not quite sure how I should manipulate the 75 g of solution.

 

[Borek]

0.49B + 0.51P = n

second equation must contain masses of both gases - what is a mass of 0.49B?