b+c/10=c+a/15=a+b/11
设b+c/10=c+a/15=a+b/11=k
则
b+c=10k---(1)
c+a=15k---(2)
a+b=11k---(3)
[(1)+(2)+(3)]/2-(1)
a=8k
[(1)+(2)+(3)]/2-(2)
b=3k
[(1)+(2)+(3)]/2-(3)
c=7k
a+b+c=8:3:7