8_1/6 - 5/18 = 49*3/18 - 5/18 = 142/18
142/18 : 14/27 = 142/18 * 27/14 = 71*3/14 = 213/14
10_7/8:3/4 = 87/8 * 4/3 = 29/2
29/2 * 2/3 = 29/3
5_3/7 : 6_1/3 = 38/7 : 19/3 = 38/7 * 3/19 = 6/7
29/3 + 6/7 = (29*7 + 6*3)/(3*7) = 221/21
221/21 * 3/17 = 13/7
213/14 - 13/7 = 213/14 - 26/14 = 187/14 = 13_5/14