Imagine somebody who is studying differential equations. He comes to the section on first order linear differential equations. He attempts to do the first problem in the section, but he comes up with the wrong answer. He then posts the problem and his answer to Math Stack Exchange. Somebody points out his error, which is something like an algebra error.
He then tries the next problem in the section. He does the problem but the answer is wrong. If he were to post the second problem and his incorrect answer to Math Stack Exchange, would that be okay? Would it be a duplicate question?