To answer this question we need to divide the hours needed to complete work (200) by how much a person works a week (35). The key aspect of this question that catches people out is that when dividing 200 by 35 we don't end up with an integer (whole number), but this is what the question asks for (since you can't have a fraction of a person).
200/35 = 5.71 to 2 decimal places. However, in order to complete this question we need an integer, which would be either 5 or 6. Since the question requires at least 200 hours to be completed the answer is 6, as 5 people wouldn't be able to complete the 200 hours needed.