Resolve everything into components normal to the plane and parallel to

the plane (then ignore the components normal to the plane)

To me this looks like it leaves you with the equation if the block is about

to move up the plane (frictional force act down the plane):

P*cos(x)-mu*sqrt(3)*30g-30g=0

and if about to move down the plane (friction acts up the plane):

P*cos(x)+mu*sqrt(3)*30g-30g=0

(you will have to check that these are the equations that you get

also check that you dont lift the block off of the plane).

RonL