Answer: Hello there!
A 15% discount means that you are subtracting 15% of the total price for some product or service. If the price of the service is X, then you need to subtract 0.15*X and that is your discount, and the "sales price" is X - 0.15*X = X*0.85
Now let's analyze the options one by one.
A) Regular price $680 and sales price = $578
let's prove this: $680*0.85 = $578
This could be a deal offered during a sale.
B) regular price is $1,120 and sales price :$896
Same procedure as before: $1120*0.85 = $952
The discount in this option is greater than 15%, then this option does not apply
C) regular price $340 sales price $289.
Same procedure: $340*0.85 = $289
This ioption does apply
D) regular price $250,sales price: $212.50
Same procedure: $250*0.85 = $212.5
This option also applies.
Then the correct options are A, C, and D.