若m,n满足m+2n=8,2m+n=7,则m+n=
问题描述:
若m,n满足m+2n=8,2m+n=7,则m+n=
答
m+2n=8,
2m+n=7
两式相加
3m+3n=15
3(m+n)=15
m+n=5