(19+1/17)*7/18=(18+1+1/17)*7/18=(18+18/17)*7/18=18*7/18+18/17*7/18=7+7/17=7又7/17
1/(13/26又26/29)= 1/[13/(26*29+26)/29]=1/(13/26*30/29)=1/(13*29/26*30)=26*30/13*29=60/29
(19+1/17)*7/18=(18+1+1/17)*7/18=(18+18/17)*7/18=18*7/18+18/17*7/18=7+7/17=7又7/17
1/(13/26又26/29)= 1/[13/(26*29+26)/29]=1/(13/26*30/29)=1/(13*29/26*30)=26*30/13*29=60/29