This is the correct answer above:
Formula is:
Sell Price = Cost / (1- Margin %).
In your example, 24.9/(1-.85) will give you a selling price of 166.
Here is the excel function: =A2/(1-B2) where A2=cost and B2=margin% (in decimal form)
(isn't that a high margin Mr. T? you're lucky to be able to do that)
100/15 * cost is the same as 24.9 * 100/(100-85) which works but is complicated.
Sell Price = Cost * (1+ Margin %) does not work.