The discount percentage can be calculated by finding the difference between the original price and the sale price, and then dividing that difference by the original price.
In this case, the original price of the water heater is $660, and it is on sale for $429.
To find the discount amount, subtract the sale price from the original price:
$660 - $429 = $231.
Next, divide the discount amount by
the original price: $231 / $660 = 0.35.
To convert the decimal to a percentage, multiply by 100: 0.35 *
100 = 35%.