Another way to do this can be to set the system up and then reduce the matrix to row-reduced echelon form.
To start with,
S = 0.6S + 0.4C + 0.1R
C = 0.3S + 0.2C + 0.4R
R = 0.1S + 0.4C + 0.5R
S + C + R = 1
We can make this into a system of equations:
-0.4S + 0.4C + 0.1R = 0
0.3S + -0.8C + 0.4R = 0
0.1S + 0.4C + -0.5R = 0
S + C + R = 1
This can be solved with a single command with MATLAB-like programs:
octave:15> B2 = [-0.4 0.4 0.1 0; 0.3 -0.8 0.4 0; 0.1 0.4 -0.5 0; 1 1 1 1 ]
B2 =
-0.4000 0.4000 0.1000 0
0.3000 -0.8000 0.4000 0
0.1000 0.4000 -0.5000 0
1.0000 1.0000 1.0000 1.0000
octave:16> rref(B2)
ans =
1.0000 0 0 0.3810
0 1.0000 0 0.3016
0 0 1.0000 0.3175
0 0 0 0
Thus,
S = 0.3810
C = 0.3016
R = 0.3175