
The arithmetic is obviously correct, your calculator could have told you that.
My question: why are you making that calculation?

I am not sure what you mean? Is the answer correct?

No.

Could anyone please correct me?

Experiment with the numbers until you find a reasonable answer.
Hint: $500 is too much.

Is it 490.25 or 399.99?

Actually the answer is correct
profit = 516387 = 129
markup based on selling price = 129/516 = .25
markup based on cost price = 129/387 = .33..
I just wanted Heyhi to explain to me why he performed that calculation.
He seems to be obsessed only with the answer, whereas I am more obsessed with
the analysis and procedure to obtain that answer.
Secondly, most of his problems dealt with markups based on selling price, which is unusual. Of course if a profit is made then the markup based on selling price is always lower than the markup based on cost price. Perhaps the business wants to give the impression of a lower markup?

Thanks, Reiny. I was wrong and barking up the wrong tree.

Yeah, I think that he was using a formula that's in my textbook, which if there's 25% off a selling price, take the selling price and divide by
100%  discount percentage. So, $387/75% = $516.