6pq-9+7pq^2-5pq+4+pq^2

Group like terms:

7pq^2+pq^2 + 6pq-5pq-9+4

Now group similar terms:

7pq^2+pq^2+pq-5 (I subtracted 5pq from 6pq and added - 9+4)

8pq^2+pq-5 (This is your final answer since you cannot simplify any further)