原方程可化为100*{(X+X*20%)-[(1200-X)-(1200-X)*20%]}=40%*100100*120%X-100*[(1200-X)-(1200-X)*20%]=40120X-100*80%*(1200-X)=40120X-96000+80X=40200X=96040X=480.2∴原方程的解为X=480.2 .