The answers is -36 because you only have to add all the numbers (you only add a negative number when is the same sing y is not negative you don’t have to add you have to subtract the number) hope it helps
If im not wrong, if every question is 2 points of 100 points in total means that are 50 questions, so if he gets 10 wrong then he would be losing 20 points which his final grade would be 80!