Question

Please Help, or Teach me.
i miss this lesson today and
this was the given assignment.



1.) 2a+b a+4b a-7b
___________ - ____________ - ____________
a^2-3ab+2b^2 a^2-4ab+3b^2 a^2-5ab+6a^2



2.) 6m 2n
____________ - ___________
m^2+5m+6 m^2+6m+9


3.) m+2 m
_____ - _____
3m+15 5m+25

Thanks in Advance