Kevin is a songwriter who collects royalties on his songs whenever they are played in a commercial or a movie. Kevin will earn $50 every time one of his songs is played in a commercial and he will earn $150 every time one of his songs is played in a movie. Kevin's songs were played on 6 more commercials than movies, and his total earnings on the royalties from all commercials and movies was $900. Graphically solve a system of equations in order to determine the number of commercials, x, and the number of movies, y, on which Kevin's songs were played.