Greetings!
[tex]mr+ns-nr-ms[/tex]
Rearrange.
[tex]mr-nr-ms+ns[/tex]
Factor by grouping.
[tex]r(m-n)+s(-m+n)[/tex]
Multiply the expression by -1.
[tex]r(m-n)-1(+s(-m+n))[/tex]
Simplify.
[tex]r(m-n)-s(m-n)[/tex]
Find the GCF.
[tex](m-n)(r-s)[/tex]
Hope this helps.
-Benjamin
