Posted by **LC** on Monday, October 29, 2012 at 11:49pm.

I thought it was similar so I wrote...

x + y = 30cm^3

x + 2y = 61.5cm^3

i.e

2x + 2y =60cm^3

x + 2y = 61.5cm^3

therefore

x= -1.5cm^3(volume of methane)

and

y= {61.5-(-1.5)}/2= 31.5cm^3(volume of ethane)

However my teacher said the volume i got for ethane is wrong, because my second equation(x+2y) should not be equal to 61.5cm^3.... so this is why I am lost. I tried to follow your previous example though. So I need your help again.

As a hint she she gave us this...

61.5cm^3- (A + 2B)= 100- (2A+ 3 and a 1/2B)...I have no idea what this is.