20-18.6: 6 11/15-4 3/20

20 - 186/10 * 15/101 - 83/20 = 20 - 279/101 - 83/20 = 20 - 5580/2020 - 8383/2020 = 20 - (- 2803/2020) = 40400/2020 + 2803/2020 = 43203/2020= 21  783/2020