1. 2 - 1 23/35 = 2 - 58/35 = (70 - 58)/35 = 12/35.
2. 9/25 : 12/35 = 9/25 * 35/12 = (9*35)/(25*12) = (3*7)/(5*4) = 21/20.
3. 11/30 + 21/20 - 1 1/3 = (22 + 63)/60 - 4/3 = 85/60 - 4/3 = 17/12 - 16/12 = 1/12.