a + b = 25
a) maximum score is a correct answer for 25 questions that means: 25 * 3 = 75 points
b) minimum score is an incorrect answer for 25 questions that means: 25 * 2 = - 50 points
c) a + b = 15
15 - 10 = 5 incorrect
10 * 3 - 5 * 2 = 30 - 10 = 20 points
d) a + b = 21
21 - 6 = 15 incorrect
6 * 3 - 15 * 2 = 18 - 30 = - 12 points
