a,3x+3y-2xy=7b,xy+2x+y+11=0c,xy+x-y=4d,2x.(3y-2)+(3y-2)=12e,3x+4y-xy=15f,xy+3x-2y=11g,xy+12=x+yh,xy-2x-y=-6i,xy+4x=25+5yii,2xy-6y+x=9iii,xy-x+2y=3k,2.x^2.y-x^2-2y-2=0l,x^2.y-x+xy=6
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