(9991乘1999.1999+9991.9991乘1999)除以2.0002
=（9991×1999×1.0001+9991×1.0001×1999）/2.0002
=9991×1999×2.0002/2.0002
=9991×1999
=19972009
（170+1/12）÷13
=(169+13/12)÷13
=169×1/13+13/12×1/13
=13+1/12
=157/12
8888008*（1/8）*1000
=1111001000