I have a question on #6, part c. Also, I need clarification if the other problems question 6 are correct.

Use the elimination method to find the solution to the system of equations. 2x - 3y = -9 -x + 3y = 6

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Satchi found a used bookstore that sells pre-owned dvds and cds. dvds cost $9 each, and cds cost $7 each. satchi can spend no more than $45.