Answer:
525%
Step-by-step explanation:
The relationship between the variables is ...
cost + markup = selling price
cost + 84%(selling price) = selling price
cost = selling price(100% -84%) = 16%(selling price)
Then the markup based on cost is ...
markup/cost = (84%(selling price))/(16%(selling price)) = 84/16
markup/cost = 5.25 = 525%