42×41/43=（43-1）×42/43=43×42/43-1×42/43=42-42/43=41又1/431/8×1/12+1/3×1/8=1/8×（1/12+1/3）=1/8×5/12=5/964/11×10+4/11=4/11×（10+1）=4/11×11=4
