[{"id": 1, "type": "short_answer", "skill": "addition", "question": "Calculate: 51 + 41", "difficulty": "medium", "explanation": "Add by place value, regrouping as needed.", "needs_review": false, "correct_answer": "92"}, {"id": 2, "type": "multiple_choice", "skill": "addition", "options": ["102", "97", "92", "91"], "question": "What is the sum of 51 and 41?", "difficulty": "easy", "explanation": "51+41=92", "needs_review": false, "correct_answer": "92"}, {"id": 3, "type": "true_false", "skill": "properties", "question": "The commutative property means 51+41 = 41+51.", "difficulty": "easy", "explanation": "The commutative property states changing the order of addends does not change the sum.", "needs_review": false, "correct_answer": "True"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 12 × 9", "difficulty": "medium", "explanation": "Multiply: 12×9=108", "needs_review": false, "correct_answer": "108"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 18", "difficulty": "medium", "explanation": "Multiply: 6×18=108", "needs_review": false, "correct_answer": "108"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 2 × 19", "difficulty": "medium", "explanation": "Multiply: 2×19=38", "needs_review": false, "correct_answer": "38"}, {"id": 7, "type": "short_answer", "skill": "computation", "question": "Calculate: 11 × 18", "difficulty": "medium", "explanation": "Multiply: 11×18=198", "needs_review": false, "correct_answer": "198"}, {"id": 8, "type": "short_answer", "skill": "computation", "question": "Calculate: 10 × 7", "difficulty": "medium", "explanation": "Multiply: 10×7=70", "needs_review": false, "correct_answer": "70"}]