[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 90 + 28", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "118"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Identity property", "Commutative property", "Distributive 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: 12 × 20", "difficulty": "medium", "explanation": "Multiply: 12×20=240", "needs_review": false, "correct_answer": "240"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 18 × 13", "difficulty": "medium", "explanation": "Multiply: 18×13=234", "needs_review": false, "correct_answer": "234"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 17 × 2", "difficulty": "medium", "explanation": "Multiply: 17×2=34", "needs_review": false, "correct_answer": "34"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 3", "difficulty": "medium", "explanation": "Multiply: 6×3=18", "needs_review": false, "correct_answer": "18"}, {"id": 7, "type": "short_answer", "skill": "computation", "question": "Calculate: 15 × 4", "difficulty": "medium", "explanation": "Multiply: 15×4=60", "needs_review": false, "correct_answer": "60"}, {"id": 8, "type": "short_answer", "skill": "computation", "question": "Calculate: 10 × 2", "difficulty": "medium", "explanation": "Multiply: 10×2=20", "needs_review": false, "correct_answer": "20"}]