Answer:
$ 5,621
Explanation:
$20,000 + 15% = 20000*1.15 = $23,000
Then we deduct the $21 assuming this has been done in a trade.
$23,000 - $21 = $22,979
So, she sells it at $28,600 - $22,979 = $ 5,621
Of course, this question is wholly written ambiguously. It's unclear if she buys $20,000 of stock, and pays a $3,000 commission which reduces her investment by that amount, or vice versa.
In any case, if you read it differently just change the numbers and multiply by .85, the rest you can figure out, just follow the logic.
That is not her Net proceeds; your teacher or whoever asked this question knows nothing about capital gains taxes. She will have to pay taxes. In 2021 and 2022, the capital gains tax rate is 0%, 15%, or 20% on most assets held for over a year. Capital gains taxes on assets held for a year or less correspond to ordinary income tax brackets: 10%, 12%, 22%, 24%, 32%, 35% or 37%