Find the missing length. The triangles in each pair are similar. Solve 15 and 16

The diameter of a circular chip is doubled to use in a new board game. the area of the new chip will be

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?

Which number completes the inequality? 2/3 < _ < 7/9