Question

What is the sum of 5x^2y and (2xy^2 + x^2y)

Answer 1

Recognize that you must combine "like" terms.  5x^2y and x^2y are "like" terms.

Adding them together, you get 6x^2y.  

Now add 2xy^2 to 6x^2y.  These are NOT "like" terms, so you end up with 
6x^2y+2xy^2 as your final answer.  This answer is acceptable as is.  

However, you could factor out the common factors:  2xy(3x+y).