Question: how can I solve these equations in maple without recursive assignment error?

I can solve three equations for x like this

x := y/p:
z := x*a+y*(1-b):
x := 100*z/(p*r+r);

                            /y a            \
                        100 |--- + y (1 - b)|
                            \ p             /
                   x := ---------------------
                              p r + r      

However, I dont like the fact that x is a function of y. I just want x to be a function of a, b, p and r. So I try to expreses the equations as follows:

y := p*x;
x := 100*z/(p*r+r);
z := x*a+y*(1-b);
solve(z, x);

Error, recursive assignment
Warning, solving for expressions other than names or functions is not recommended.

Any idea how I can get an equation for x that only depend on a, b, p and r? 

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