[{"id": 1, "type": "short_answer", "skill": "subtraction", "question": "Calculate: 143 − 81", "difficulty": "medium", "explanation": "Subtract by place value, borrowing as needed.", "needs_review": false, "correct_answer": "62"}, {"id": 2, "type": "multiple_choice", "skill": "subtraction", "options": ["60", "63", "62", "224"], "question": "What is 143 − 81?", "difficulty": "easy", "explanation": "143-81=62", "needs_review": false, "correct_answer": "62"}, {"id": 3, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 13", "difficulty": "medium", "explanation": "Multiply: 6×13=78", "needs_review": false, "correct_answer": "78"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 13", "difficulty": "medium", "explanation": "Multiply: 4×13=52", "needs_review": false, "correct_answer": "52"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 10 × 12", "difficulty": "medium", "explanation": "Multiply: 10×12=120", "needs_review": false, "correct_answer": "120"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 16 × 17", "difficulty": "medium", "explanation": "Multiply: 16×17=272", "needs_review": false, "correct_answer": "272"}, {"id": 7, "type": "short_answer", "skill": "computation", "question": "Calculate: 2 × 13", "difficulty": "medium", "explanation": "Multiply: 2×13=26", "needs_review": false, "correct_answer": "26"}, {"id": 8, "type": "short_answer", "skill": "computation", "question": "Calculate: 14 × 15", "difficulty": "medium", "explanation": "Multiply: 14×15=210", "needs_review": false, "correct_answer": "210"}]