The selling price of a skateboard is $147. the store has a 75% markup policy. what is the cost of the skateboard to the store?

Given:
selling price = $147
mark up = 75%

Asked:
original cost

The solution:
Selling price is the sum of the original cost and mark up price. It could be written as following,
Original cost + mark up price = selling price
100% original cost + 75% original = selling price
175% original cost = selling price
1.75 original cost = selling price

Solve for original cost
original cost = selling price/1.75

Plug in the numbers
original cost = selling price/1.75
original cost = 147/1.75
original cost = 84

The original cost of the skateboard is $84