A horizontal force of P=150N is just sufficient to hold the crate from sliding d

Question

A horizontal force of P=150N is just sufficient to hold the crate from sliding down the plane, and a horizontal force of P=330N is required to just push the                     crate up the plane. Determine the coefficient of static friction between the plane and the crate, and find the mass.
                    
                    

I understand the equations I need to solve for are:

150cos30 + ?Wcos30 + 150? sin30 = Wsin30

and

350cos30 = Wsin30 + ?Wcos30 + 350? sin30

But how do I solve them? There are two different variables and I don't have the mass of the crate. And if I assume W = 9.81 then I get -1.96 as my coefficiant of friction, which is obviously wrong.

Any help with this is appreciated.

Explanation / Answer

alrigth

150cos30 + ?Wcos30 + 150? sin30 = Wsin30 ,

350cos30 = Wsin30 + ?Wcos30 + 350? sin30

W= 415.139

and

u =0.178

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