(1)x+y+z=50,1500x+2100y+2500z=90000
∵均大于0而小于50的整数
∴x=27,y=20,z=3;x=29,y=15,z=6;x=31,y=10,z=9;x=33,y=5,z=12
(2)设购买电视机甲种x台,乙种y台,丙种z台,由题意得:
①x+y=50,1500x+2100y=90000,
解得x=25,y=25;
②y+z=50,2100y+2500z=90000,
解得y=87.5,z=-37.5,(舍去)
③x+z=50,1500x+2500z=90000,
解得x=35,z=15.