Aschool purchase boxes of candy bars
each box contains 50 candy bars
each box cost $30
how much does the school have to charge for, each candy bar to make a profit $10 per box

Ok so, we need a profit of $10 per box, so we can assume the boxes are (fake) valued as $40 (per box)

since each box has 50 bars, we set up a simple proportion 



50($ money) = 40
$ = 40/50
$= .8

the school will have to sell the bars for $0.80

Ill say thats a GREAT deal :3

The answer to your question is the last one