（2/3）*6/（8/9）=?
=6*(2/3)*(9/8)
=6*3/4
=9/2
（3/4）/（6/7）/14
=(3/4)/[(6/7)/14]
=(3/4)/[(6/7)*(1/14)]
=(3/4)/(1/12)
=3/4*12
=9
（9/10）/（1-（3/8））
=(9/10)/1-[(9/10)/(3/8)]
=(9/10)-[(9/10)*(8/3)]
=(9/10)-(12/5)
=(9-24)/10
=-15/10
=-3/2
(1/5)+(4/5)*(15/16)
=(1/5)+3/20
=(4+3)/20
=4/20
=1/5
(17/2)/15*(5/7)
=(17/2)*1/15*5/7
=17/42
(6/5)/4*(2/3)/(1/6)
=(6/5)*1/4*(2/3)*6
=6/5
）是一个分数