Final answer:
The correct expression to find the discount cost of any item with a 30% discount is the original price minus 30% of the original price, which is option (b).
Step-by-step explanation:
To find the discount cost for any item during a store sale with a 30% discount, we need to use an expression that deducts the discount amount from the original price.
The correct expression is: Discount Cost = Original Price - (Original Price × 0.30)
This formula first calculates the amount of discount by converting the percentage to a decimal (30% becomes 0.30) and then multiplying it by the original price. After finding the discount amount, we subtract it from the original price to get the price after the discount has been applied.
Considering option (a), it incorrectly represents the discount amount, not the discounted cost. Option (c) incorrectly suggests adding the discount to the original price, and option (d) suggests dividing the original price by 0.30, which is also incorrect.