[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 90 + 90", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "180"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Distributive property", "Commutative property", "Identity property", "Associative property"], "question": "Which property states a+0=a?", "difficulty": "easy", "explanation": "The identity property of addition states that adding 0 to any number gives that number.", "needs_review": false, "correct_answer": "Identity property"}, {"id": 3, "type": "short_answer", "skill": "computation", "question": "Calculate: 8 × 10", "difficulty": "medium", "explanation": "Multiply: 8×10=80", "needs_review": false, "correct_answer": "80"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 3 × 13", "difficulty": "medium", "explanation": "Multiply: 3×13=39", "needs_review": false, "correct_answer": "39"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 2", "difficulty": "medium", "explanation": "Multiply: 6×2=12", "needs_review": false, "correct_answer": "12"}]