(-1/24)/(1/6-1/8+1/12)=[(-1/24)*24]/[(1/6-1/8+1/12)*24]=-1/[1/6*24-1/8*24+1/12*24]=-1/3
(-1/24)/(1/6-1/8+1/12)=-1/(1/6×24-1/8×24+1/12×24)=-1/（4-3+2）=-1/3
