1.设这桶油共x克.则9+(x-9)*4/11+x/2=x 解得,x=30
2.设共进x 台.2/5x+3/5*1/2x+2/5*2/3x+30=x 解得,x=900
3.设一班x人,二班y人.联立方程组(x+y=96 ,3/4x+3/5y=66)解得,x=56,y=40
4.设六年级原有学生x人.7/12x+15=3/5(x+15) 解得 x=360
5.设合唱队现有男生x人,女生y人.联立方程组{5/6(y-3)=x, x=5/12(x+y)} 解得x=15,y=21
6.设ABC花房原来分别有x、y、z盆花.则x+y/3=200,(1-1/5)z=200,x+y+z=600 解得,x=125,y=225,z=250