x/2=y/3=z/0.5=2zx=4z, y=6z.(x+3y-z)/(2x-y+z)=(4z+18z-z)/(8z-6z+z)=21z/3z=7.
设 2分之X等于3分之Y等于0.5分之Z=kx=2ky=3kz=k/2(x+3y-z)/(2x-y+z)=(2k+9k-k/2)/(4k-3k+k/2)=(21k/2)/(3k/2)=7