Question: how to use results from "solve"

I solve a system of equations, and am having difficulty 1) understanding what I"m seeing, 2) using the results.
 

Download substitution_help.mw

 

At (21), I get the solution to the system of equations.  I then want to use substitute a value for xC1 that supports the solution, and plug it into the other variables that are solved in terms of it.  However, I can't figure out how to do this.  I keep getting errors like:

Error, invalid input: eval expects its 2nd argument, eqns, to be of type {integer, equation, set(equation)}, but received {Rsrc = .9640102828*xC1^2+0.2570694087e-2*(140625.*xC1^4-151321.*xC1^2)^(1/2), xC2 = -0.1333333333e-2*(281250.*xC1^3+750.*xC1*(140625.*xC1^4-151321.*xC1^2)^(1/2)+51018750.*xC1^2+136050.*(140625.*xC1^4-151321.*xC1^2)^(1/2)-151321.*xC1)/(375.*xC1^2+(140625.*xC1^4-151321.*xC1^2)^(1/2)), xC1 <= -363.3194071}

please see attached file.

I assume I'm getting 2 solutions.  I'm picking the first one and trying to then solve for the other variables once I pick a value for xC1.

 

Thank you,

substitution_help.mw

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