I am looking for help getting started. I was told to do this by hand and wanted to be pointed in the direction of a starting point.
d/dx = partial diff
3*dA/dx + 2dB/dx + 3*dA/dy + 7dB/dy + 2 dC/dy = 1
2*dA/dx + 2dC/dx + 2*dA/dy + 2dB/dy + 6 dC/dy = 0
3*dA/dx + dB/dx+ dC/dx + 3*dA/dy + 5dB/dy + 4 dC/dy = 4
IC @ y=0 A=x, B=2x, C=3x