The difference between the selling price and the cost price is the profit he earned.
Profit = Selling Price - Cost Price
Profit = $216 - $180
Profit = $36
To find the percentage profit, we need to calculate what proportion of the cost price the profit represents, and express that as a percentage :
Percentage Profit = (Profit : Cost Price) * 100%
Percentage Profit = ($36 : $180) * 100%
Percentage Profit = 0.2 * 100%
Percentage Profit = 20%
Therefore, his percentage profit is 20%.