Cost of good sold (formula to work out how much to sell item for?)

Hi there im trying to write a formula but cant for the life of me
Its for a Cost of good sold chart.I have the all the fields for my cost & another one with a sum formula to add it up.

I want to know how much to charge for my product. ( ie the cost of goods sold IE £10 is 20% of the full good sold ). Which means that i need to sell my product at £50 to make that 20%. ( i know this off by heart not by doing any formula)

how would i write a formula that showed me how much i would need to see my goods for if i already knew the percentage (20%) & cost of goods. (£10)

Thanks very much for your time.

Try: =10/0.2