नेहाने प्रश्नपत्रिकेतील 18 प्रश्न सोडवले, बरोबर उत्तराबद्दल प्रत्येकी 5 गुण मिळून व चुकीच्या उत्तराबद्दल प्रत्येकी 1 गुण कापला जाऊन तिला एकूण 78 गुण मिळाले. तर तिने किती प्रश्न बरोबर सोडवले ?

The correct answer is Option D (16).

Key Points:
• Exam Marking System Simultaneous Equations:
• Step-by-step mathematical calculation:
• 1. Total questions attempted = 18.
• 2. Let the number of correct questions = C.
• 3. Then the number of incorrect questions = 18 - C.
• 4. Marking scheme: +5 marks per correct answer, -1 mark per incorrect answer.
• 5. Total marks obtained = 78.
• 5C - 1(18 - C) = 78
• 5C - 18 + C = 78
• 6C = 78 + 18
• 6C = 96
• C = (96)/(6) = 16
• Verification: 16 correct (16 × 5 = 80 marks) and 2 wrong (2 × 1 = 2 marks deducted) 80 - 2 = 78 marks (Verified)!
• Matches Option (4) 16.
• Key Takeaway: Equation: 5C - (18 - C) = 78 6C = 96 C = 16 correct questions.