1、0-(+1/3)-(+1/6)-(-1/4) =-1/3-1/6+1/4 =-1/2+1/4 =-1/4 2、(-3/5)x(-7/8)x(2又1/2) =-3/5x5/2x7/8 =-3/2x7/8 =-21/16 3、30x(-1/4)x(2/15) x(-4/5) =(30x2/15)x(1/4x4/5) =4x1/5 =4/5