若3x+2y=54,2x+3y=46,则x+y=()

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 若全集I={(x,y)|x,y∈R},集合M={(x,y)|(y-3)/(x-2)},N{(x,y)|y=x=1},则( 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 若3x-4y=0,则x/y=______,（x-y)/y=______,（3x+2y)/(2x+3y)=_____. 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 若x,y满足|2x-y-3|+|3x+2y+1|=0,则x= y= 若2x+3y=2004,则代数式2(3x-2y)-(x-y)+(-x+9y)=... 若5x+3y=3x+4y=x+2y+6,则x+y=___ 若2x+y=2012,则代数式2(3x-2y)-(x-y)+(-x+9y)=