I have a calculator that does this for me but I want to know the equations

i.e..
my cost is $1.85
the sell price is $20

the cost to sell price is a 90.75% increase
my profit is $18.15

on my calculator I just push those buttons but I want to know the equation for figuring it out

and

if the cost is $0.89
and my margin is 90.75%
then the sales price is $9.62

what are the equations for these

:confused::confused::confused::confused::confused:

Thank you for your help:)

Okay:

Profit = Sales price – cost

Cost to sales price (aka Margin) = profit / sales price


Last one is complex to solve; I tried to derive the formula but I was unable to. Could someone good a deriveing formulas please help?