Answer:
(x+3)+(5+3y)
Step-by-step explanation: In the equation, when you have four terms you group like terms. So 5x+15 by itself and work it out which you will get 5(x+3) and do the same for 3xy+9y answer is 3y(x+3).
Then you will say 5(x+3)+3y(x+3) and then you'll
5(x+3)/(x+3)=5 because you will cancel the (x+3) so the answer would be 5
You will do the same for 3y(x+3)/(x+3)
you will get 3y
Finally, you will take the first equation which is (x+3), and then you'll use the last equation which is (5+3y)
So that's how you will get (x+3)+(5+3y)