\(20:10=2\); \(6\cdot10=60\); \(100:50=2\); \(10\cdot8=80\); \(100:20=5\); \(8\cdot10=80\); \(10\cdot40=400\); \(20\cdot20=400\); \(60:30=2\); \(70:10=7\); \(200:10=20\); \(90:30=3\).