How do you greet your peer? Is that different from how you greet your elder?

I would greet my friend with, "ahn young" (안녕). I would not greet my elder the same way because this is informal. The formal way to greet my elder would be, "ahn young ha sae yo" (안녕하세요).

(4/5)^5=?

((4*4*4*4*4)/(5*5*5*5*5)) = 1024/3125

-18+4(6/2)=?

-18+4(3)= -18+12= -18+12= -6