[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 60 + 99", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "159"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Commutative property", "Distributive property", "Associative property", "Identity 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: 9 × 15", "difficulty": "medium", "explanation": "Multiply: 9×15=135", "needs_review": false, "correct_answer": "135"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 3 × 9", "difficulty": "medium", "explanation": "Multiply: 3×9=27", "needs_review": false, "correct_answer": "27"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 13 × 4", "difficulty": "medium", "explanation": "Multiply: 13×4=52", "needs_review": false, "correct_answer": "52"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 18 × 14", "difficulty": "medium", "explanation": "Multiply: 18×14=252", "needs_review": false, "correct_answer": "252"}, {"id": 7, "type": "short_answer", "skill": "computation", "question": "Calculate: 8 × 2", "difficulty": "medium", "explanation": "Multiply: 8×2=16", "needs_review": false, "correct_answer": "16"}, {"id": 8, "type": "short_answer", "skill": "computation", "question": "Calculate: 11 × 7", "difficulty": "medium", "explanation": "Multiply: 11×7=77", "needs_review": false, "correct_answer": "77"}]