Evan is trying to save his money to buy new parts for his bike. he has saved $27, which is 45% of what he needs so far.

I imagine the part you left off was "how much does he need to fix his bike?"  Either how much more, or how much altogether.  No matter.  We will turn those words into a mathematical expression.  "$27 is 45% of how much money?" looks like this: 27=.45x.  Divide both sides by .45 to solve for x.  x = 60.  So he needs 60 total, of which he still needs 60-27 = 33

its b because when subtract 30-24=6