Final answer:
To calculate the total cost including a 20% tip on a $30 manicure, you multiply $30 by 0.20 to find the tip amount ($6), and then add it to the original cost, resulting in a total of $36.
Step-by-step explanation:
Brianna went to get a manicure that cost $30. To calculate a 20% tip, we convert the percentage to a decimal by dividing by 100, which gives us 0.20. Then, we multiply the cost of the manicure by the decimal form of the tip:
$30 × 0.20 = $6
Now we know the tip amount Brianna wants to leave is $6. To find the total cost including the tip, we add the tip to the original cost of the manicure:
$30 + $6 = $36
Therefore, the total cost Brianna will pay, including the tip, is $36.