How do I solve for b-9-b=-18

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?

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.

Find the measure of the angle indicated in bold