To calculate 20% off $30, multiply $30 by 20% (0.20). This equals $6. Subtract $6 from $30, giving a final price of $24. Therefore, 20% off $30 reduces the total cost to $24.
To calculate 20% off of $30, first find 20% of 30 by multiplying 30 by 0.2, which equals 6. Then, subtract this amount from the original price: 30 minus 6 equals 24. So, after applying the 20% discount, the final price is $24.