[slm1990]

I've been trying to solve this exercise for about an hour now, and still cannot figure out how.
So here it is:
Below are shown measurements of density (D) of cyclohexane and pentadecane mixture as a function of mole fraction of cyclohexane (Xc), at 298.15 K:

Xc            :  0.6965  0.7988  0.9004
D/ gcm^-3 :  0.7661  0.7674  0.7697   

Partial molar volumes of each component at Xc = 0.7988 need to be computed.

Can anyone explain briefly how can I solve this?
Thanks