Total possible marks = 20x6 = 120
For each wrong answer, Jane loses the 6 points she could have
gotten as well as 3 more points.
Total deduction per wrong answer = 3+6 = 9
Total marks deducted from wrong answers = 120-75 = 45
Number of wrong answers = 45/9 = 5
Total correct answers = 20-5 = 15