CHEMISTRY HELP!!!!!!

A gas X dissociates on heating to set up the following equilibrium:
X(g) --> Y(g) + Z(g)
A quantity of X was heated at constant pressure, p, at a certain temperature. The equilibrium partial
pressure of X was found to be 1/7 p. What is the equilibrium constant, Kp at this temperature?

How do you work this out? Please

Hi!!
let x be the degree of dissociation of X
now
X(g) --> Y(g) + Z(g)
initial p ---- ----
at equilibrium p(1-x) px px

Now at eq. partial pressure of X=p/7
and total pressure at eq. =p(1+x)
now p/7=p(1-x)/p(1+x)
or p/7=(1-x)/(1+x)
or px+p=7-7x
or x(p+7)=7-p
or x=(7-p)/(7+p)
now Kp= (Py)(Pz)/(Px)
or Kp=px*px/p(1-x)=px^2/(1-x)
or Kp= p*{ (7-p) / (7+p) }^2/(1-{ (7-p)/(7+p)})
solve it and you will have the answer.