Solve the right triangle

What is the name used to describe a graph where for some value of x, there exists 2 or more different values of y?

Find the solution of this system of equation -7x+y=-20 9x-3y=36

Hector and alex traded video games. alex gave hector one fourth of his video games in exchange for 6 video games. then he sold 3 video games and gave 2 video games to his brother. alex ended up with 16 video games. how many video games did alex have when he started?