Question

taking, p(a) be the vapour pressure of a, x(a) be its mole fraction, and p(a)0 be the vapour pressure of the solvent in its pure form"

Answer 1

I think the question is not complete but i would like to tell you all the information that can be drawn from this is

P(a)0*x(a)=p(a)

You can ask if any other doubt related to this in the comments

Thanks