设x=2k y=3k z=4k
则 3x+2y-3z/x+y+z=(9k+6k-12k)/(2k+3k+4k)=3k/9k=1/3
a+b/4=a+c/9 所以b/4=c/9 b=4c/9 代入a+b/4=b+c/7
a=3b/4+c/7=3*4c/36+c/7=10c/21
所以
b:c=4:9=28:63
a:c=10:21=30:63
a:b:c=30:28:63