1) (-4/15+5/9):(-26/45)=приводим к общему знаменателю 45
(-12+25)/45 : (-26/45) = -13/45 * 45/26 = -1/2
2) -12:(-2 1/13)+1 1/4:(-15/46)=12: 27/21 - 5/4 * 46/15 = 84/9 - 46/12 = (336-138)/36 = 198/36 = 33/6 = 11/2 = 5. 1/2
3) (-3 3/10-1 8/15):(-1 2/27) = (-33/10 - 23/15) : (-29/27) = ((-66-46)/30) * (-2/29) = 112/30 * 2/29 = 112/435
4) (9/20-7/8):(-7/45-2/9)= (18-35)/40 : (-7-10) / 45 = -17/40 * 45/(-17) = 9/8 = 1. 1/8