100. 140: 20, 8 100: 900, 500+(600-3*100), 560:7, 3 200:800, 9 000:(100-90)

1) $$140 : 20 = 7$$ 2) $$8100 : 900 = 9$$ 3) $$500 + (600 - 3 \times 100) = 500 + (600 - 300) = 500 + 300 = 800$$ 4) $$560 : 7 = 80$$ 5) $$3200 : 800 = 4$$ 6) $$9000 : (100 - 90) = 9000 : 10 = 900$$