Acidity I believe...sorry if I'm wrong just got on the subject
Cyclohexane - cyclic hydrocarbon with 6 carbon atoms.
2 methyl groups (-CH3) on carbon atom number 1
Hope it helped!
1/2 - 3/7 = 7/14 - 6/14 = 1/14
That new volume will be 0.25 L. You use the formula P1V1 = P2V2.