2分之X=3分之Y=4分之Z那么X+Y-Z分之3X-Y+4Z=?x/2 =y/3 =z/4令上式=k，即 x/2 =y/3 =z/4=k，可得x=2k，y=3k，z=4k，所以(3x-y+4z) / (x+y-z)=(6k-3k+16k) / (2k+3k-4k)=19k / k=19
