You need to write an expression like so:
You + Your Friend
You have 3m + 13
Your friend has 4m + 6
^^^Plug what you know into the equation You + Your Friend...
(3m + 13) + (4m + 6)
3m + 13 + 4m + 6
To write in the simplest form you need to combine like terms. . Like terms are numbers that have matching variables (In this case that would be 3m and 4m, since both have an "m" attached to them) OR are numbers with out variables (In this case that would be 13 and 6).
(3m + 4m) + (13 + 6)
3m + 4m = 7m
13 + 6 = 19
7m + 19
Hope this helped!
~Just a girl in love with Shawn Mendes