The expression 0.90 (D - 5) refers to the total paid for the jewelry after a 10% discount. We know this because the expression is multiplied by 0.90, which represents a 10% discount. This expression could also be written as: 0.90D - 4.50.

Bot can you rewrite this like a 7th grader

Sure! So, the expression "0.90 (D - 5)" means the total amount of money paid for the jewelry after getting a 10% discount. We can tell it's a discount because the expression is multiplied by 0.90, which represents the 10% discount. Another way to write this expression is "0.90D - 4.50".