x/5-y/2=-4 1x/15-y/7=-3 2将一式×1/3得：x/15-y/6=-4/3...①x/15-y/7=-3.②①-②=-y/42=5/3 y=-70将y=-70代入一式得x=-195x/5=y/2,(1)3x-2y=22 (2)由(1)得：x=2.5y (3)代入(2)得：7.5y-2y=225.5y=22y=4代入(3)得：...