To calculate 20% off of 30 dollars, follow these steps:
1. Convert the percentage to a decimal by dividing by 100. So, 20% becomes 0.20.
2. Multiply the original amount by the decimal. In this case, 30 dollars multiplied by 0.20 equals 6 dollars.
3. Subtract the result from the original amount. So, 30 dollars minus 6 dollars equals 24 dollars.
Therefore, 20% off of 30 dollars is 24 dollars.