21 divided 6216 please find the answer

Which of the fallowing best completes the sequence 5,10,15, a) 30 b) 22 c)25 d)35

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

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?