Henleys is having a 45% off sale on air conditioners. fred pays $124 for an air conditioner. what was the original price?

Well I don't know !
Let's get together and work it out.

We don't know the original price yet, but we need to give it a name so that we can work with it in math equations and stuff.  I'm going to call it OP. 

OP was reduced by 45% before Fred came along.
That  means that 45% of OP was cut off and discarded.
How much of it was left ?
Well, before it was reduced, 100% of it was marked on the price tag.
After 45% was cut off, there was  (100% - 45%) = 55% of it left.

That's what Fred paid for the one he bought . . .  55% of OP.

                     55%  of  OP  is  $124 .

We have to change that sentence into math.

--  55%  means  0.55
--  "of" means "times"
--  "is" means 'equals sign'

So now we can write:     0.55  x  OP  =  $124

There's the equation.
Now, divide each side
by 0.55, and you get                   OP  =  $124 / 0.55

                                                        =     $225.45