từ 2x=3y->x/3=y/2
5y=7z->y/7=z/5
ta có x/3=y/2=x/3*1/7=y/2*1/7=x/21=y/14
y/7=z/5=y/7*1/2=z/5*1/2=y/14=z/10
=>x/21=y/14=z/10
x/21=y/14=z/10->3x/63=7y/98=5z/50
3x/63=7y/105=5z/50=3x-7y+ 5z/63-98+50=-30/15=-2
3x/63=-2>3x=(-2)*63->3x=-126->x=(-126):3=-42
7y/98=-2->7y=(-2)*98->7y=-196->y=(-196):7=-28
5z/50=-2->5z=(-2)*50->5z=->z=(-100):5=-20
P/s: cho xin 5 sao và câu trả lời hay nhất ạ!