How Do I create a formula for the percentage below?

[Anita]

I am trying to type a formula to get a percentage for cells B19 and B20 with
the following numbers type in these two cells - B19 - 70 and B20 - 34.5. I
actually have the answer (16.8%) but need to know the formula that would come
up with this number. Any help is appreciated. Thanks

 

[Gary''s Student]

Try this:

=(B20-22.74)/B19

 

[Anita]

Gary, Thanks, could you tell me what 22.74 means and how you came up with
that number?

 

[Gary''s Student]

It is the discount factor. It is the amount 35.4 must be discounted to
arrive at the correct percentage.

I calculated it using Goal Seek.

 

[Anita]

Wow, thanks Gary's student...if I could I'd send you the document I typed so
you can help me with additional formula questions.