math
posted by Mike .
simplify the expression by combining like terms
r + 2s + 3r

Well since both the 'r's are like terms, you'd combine them, and don't forget that there is a 1 in front of each variable, so you'd add 3 + 4 and have 4r.

OH sorry typo!
3 +1 and you'd have 4r! sorry! 
How do you combine the r's?

Nicole, Thanks but I do not understand
how do you combine the r's? 
you would combine the r's just by adding them together, because they are the same variable. The first r in the equation doesn't have a number with it, right? So since it isn't attatched to a number, pretend that there is an invisible 1 in front of it. So when you add the two r's together then you get 4r right? So pretend instead that the equation reads:
1r + 2s + 3r 
4r + 2s

exactly =)