1 =【5/4+(20/3-15/4)*7/15】*15/4
=[5/4+20/3*7/15-15/4*7/15]*15/4=[5/4+28/9-7/4]*15/4=[28/9-1/2]*15/4=235/36=6(19/36)
2 =2(2/11+2/7+5/9)÷(2/11+2/7+5/9)=2
3=1/12× (1/8+1/9+1/10+1/11﹚+(1/8+1/9+1/10+1/11﹚×﹙1/9＋1/10＋1/11﹚－﹙1/8＋1/9＋1/10＋1/11＋1/12﹚×﹙1/9＋1/10＋1/11﹚=
1/12× (1/8+1/9+1/10+1/11﹚-1/12×﹙1/9＋1/10＋1/11﹚=1/12×1/8=1/96