9 - 5/6 = 8 + 6/6 - 5/6 = 8 1/6
или
9 - 5/6 = 54/6 - 5/6 = (54-5)/6 = 49/6 = 8 1/6
6 7/15 - 3 9/10 = 6 14/30 - 3 27/30 = 2 17/30
или
6 7/15 - 3 9/10 = (97*2) /(15*2) - (39*3) /(10*3) =
= (194 - 117)/30 = 77/30 = 2 17/30
4 1/27 - 3 8/39 = 4 13/351 - 3 72/351= 1 13/351 - 72/351=
=364/351 - 72/351=292/351
или
4 1/27 - 3 8/39 = (109*13)/(27*13) - (125*9) /(39*9) =
= (1417-1125)/351 = 292/351