A baker sells a dozen donuts for $3.99. The cost to make three donuts is $0.45. How much is the total profit on 5 dozen of donuts?

Multiply $0.45 (the cost of making 3 donuts) by 4 to find the cost of making a dozen donuts: $0.45 × 4 = $1.80.
Then multiply the cost of making a dozen donuts by 5 to determine the cost per 5 dozen: $1.80 × 5 = $9.00.
Next, multiply the selling price per dozen times 5, the number of dozens sold: $3.99 × 5 = $19.95.
Finally subtract the cost of making 5-dozen donuts from the price the baker sells them for to determine the profit: $19.95 – $9.00 = $10.95.