Hi,

There are many formulas for finding cost price, but it all depends on the type of question you get. For example,

Cost price = Selling price - profit ( when selling price and profit is given )

Cost price = Selling price + loss ( when selling price and loss is given )

Cost price = 100 x selling price / 100 + profit % ( when selling price and profit % is given )

Cost price = 100 x selling price / 100 - loss % ( when sellin price and loss % is given )

So, there are totally 4 formulas for finding the cost price in a given question ( but it depends on the information given in the question ). It is easier to use these formulas than substituting the cost price with a variable.

Hope this clears your doubt,

Cheers!!!