m+n-m+n=2n
m+3-6m-5-m+1=-6m-1
(m+n)-(m-n)=m+n-m+n=(m-m)+(n+n)=n+n=2n
(m+3)-(6m+5)-(m-1)=m+3-6m-5-m+1=(6m-m+m)-(5-3-1)=6m-1
m+n-m+n=2n
m+3-6m-5-m+1=-6m-1
(m+n)-(m-n)=m+n-m+n=(m-m)+(n+n)=n+n=2n
(m+3)-(6m+5)-(m-1)=m+3-6m-5-m+1=(6m-m+m)-(5-3-1)=6m-1