Here's why: The total he could have gotten was 100%. He got a 76%, which is 24% less. If you do 24 divided by 4, the answer will tell us how many points is for each question. The answer is 6. To double check, you can do this, if each question is worth 6 points, and he misses 4 questions, that means that he loses 24% worth of points, 100 minus 24 equals 76%. I did my answer negative, because the question wants to know his change in score for each question he gets incorrect, that means his score is going down which is negative...
