Find a value before a percentage change. Could you please explain to me how you’ve got the answer too, so I can do the rest.

Trigonometry help asap

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?

Ammonia molecules have three hydrogen atoms and one nitrogen atom. how many of each atom arein five molecules of ammonia