12×30=360, 17×50=850, 100÷20=5,
84÷6=14, 212÷70≈3, 300÷50=6,
51÷7≈7, 368÷60≈6, 91÷7=13,
635÷90≈7, 200÷30≈7, 559÷80≈7.