You can put this solution on YOUR website! I am assuming that you mean 2x+3y that can't be added. Well, think of it this way. You have 2 oranges and 3 apples. You cannot possibly give a total unless you say 5 fruits. There is no fruit orange+apple. Also cannot be added because although they are both apples think of them as red and green apples. There aren't red green apples.
Hope this helps and feel free to contact me with further questions,
lyra
