(5/7+5/9)吧(9又2/7+7又2/9)除以(5/7+5/9)=(65/7+65/9)/(5/7+5/9)=13*(5/7+5/9)/(5/7+5/9)=13
(65/7+65/9)/((63+25)/45)=(65(9+7)/63)/(88/45)=65*16*45/63*88=65*90/63*11=650/77
