How do you find the original price if the percent of discount is 25% in the sales price is $40

Iwant to know what 3g+5h+4g-2h is my teacher is too selfish to tell us

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?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?