(Solved): In a ternary phase diagram, according to the representation of the mole fractions, show that along ...

In a ternary phase diagram, according to the representation of the mole fractions, show that along the line joining an apex $(Z)$ to the point from $\mathrm{P}$ to ${\mathrm{P}}^{?}$, the ratio of two of the mole fractions remain constant while mole fraction of the third component changes for $\mathrm{P}$ and ${\mathrm{P}}^{\mathrm{r}}$.