30.4-(3x+5y)=2y (1)32-(3x+5y)=2x (2) 化简原方程(1)得30.4-3x-5y=2y30.4-3x=7yy=(30.4-3x)/7 (3)化简方程（2）得32-3x-5y=2x32-5y=5x (4)把（3）带入（4）得32-5*(30.4-3x)/7=5x32*7-5*(30.4-3x)=7*5x224-152+15x=...