A takes 4 more days to complete a work than A and B working together and 5 less days to complete the same work than B working alone. How many days would A take to complete the work, if B starts working against him and starts destroying the work, considering his speed doesn't change?

Let A take x days, B take y days. A = (x+y) + 4 and A = y - 5. Thus, y = x + 5. Using work rates: 1/(x+4) = 1/x + 1/(x+5). Solving this quadratic equation x^2 - 6x - 20 = 0 leads to non-integer results, suggesting a potential error in the problem statement or interpretation. However, testing the options, 30 days fits the logic of work rates.