Formula to backout percentage markup

Hi, Trying to create formula to backout markup on tools. I have one spreadsheet (Ex A) used by the techs to quote tool amounts to customers. The second worksheet is used by office to track sales (Ex B). It's very large but here are the columns I'm concerned with.

Example A: Form to quote prices to customers (This changes every time a customer calls or comes in)

Column A (input field that sum all tool amounts) = $2,864.77
Column B (calculates 20% markup for each tool) = $572.95
Column C (Subtotal and amount quoted customer) =$3,437.72

Example B: Tool Ledger to track sales from all techs

Column A (Amount Billed Customer)= $3,437.72
Column B (formula needed ... I have: =A1*(1-0.2) which should take the amount billed customer and minus the 20% markup ($2,864.77 from ex) but it does not. It returns $2,750.17 Help?

That's the difference between MARKUP and PROFIT MARGIN
Your MARKUP is 20% but your PROFIT MARGIN is only 16.6%

Your selling price is cost plus 20% (120% of cost)
Cost x 1.2 = Sell
Your profit is selling price divided by 1.2
Sell / 1.2 = Cost
=(A1/1.2)

If you actually wanted to make 20% PROFIT you'd have to use
Cost / .80 = Sell

Thanks - I appreciate your help