For Q3, the method is actually inverse proportion, since the more people there are, the less number of days they can survive. Key word is "same amount of food". This means there is a constant "k" you need to find. Always remember that inverse proportion is the method to solve all these time questions. For Q4, you get 5 marks for one correct answer. But when you are wrong, not only will you lose 5 marks for not being correct, you also lose another 2 marks. This means for just 1 wrong answer, you get 7 less marks from 100. Since Siti got 51 marks, means she lost a total of 49 marks from 100. So we can easily find the number of questions she got WRONG and eventually find the questions she got CORRECT