The problem: "One week Trey rented 4 DVDs and 2 video games for $18. The next week he rented 2 DVDs and 1 video game for $9. Find the rental costs for each video game and DVD. Explain your answer." I know the equations (4x+2y=18, and 2x+1y=9) and the answer, but I'm really confused as to what work I should show as my teacher requires it, substitution and elimination don't work, so I don't know what to do. Please help.