Pls help do in 30 mins

You receive 15% of the profit from a car wash how much money do you receive from a profit of 300

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?

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms