Which one is the right one? I really need help im failing math

Neveah and clint are baking muffins for the bake sale. they need to bake 30 muffins for their display case. clint has baked 4 so far, and neveah has baked 7. how many muffins (m) do they have left to bake? show your work!

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?

What is the 12th term of b(n)=-4-2(n-1)