[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 90 + 38", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "128"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Associative property", "Distributive property", "Commutative 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: 16 × 12", "difficulty": "medium", "explanation": "Multiply: 16×12=192", "needs_review": false, "correct_answer": "192"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 8 × 16", "difficulty": "medium", "explanation": "Multiply: 8×16=128", "needs_review": false, "correct_answer": "128"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 8 × 13", "difficulty": "medium", "explanation": "Multiply: 8×13=104", "needs_review": false, "correct_answer": "104"}, {"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: 14 × 20", "difficulty": "medium", "explanation": "Multiply: 14×20=280", "needs_review": false, "correct_answer": "280"}]