Percent of a number: tax, discount, and more

Erika ate brunch at a restaurant. The bill came to $12,20. If she left a 15% tip, how much was the tip?

Write the percentage as a decimal.

15% = 0.15

Multiply the decimal by the amount of the bill. Multiply as you would multiply whole numbers, then write the decimal point in the answer.

The tip was $1.83.

If the sales tax rate is 10% in New York State, then how much sales tax would you pay in Albany for a $31 pair of pants?

The sales tax would be: $