题目,应该是x+y等在分子上吧
设(x+y)/7=(x+z)/8=(y+z)/9=k
则x+y=7k x+z=8k y+z=9k
就这样z=5k y=4k x=3k
就这样x+y+z=12k=12
就这样k=1
就这样x=3 y=4 z=5