`frac\{1xx3xx5+2xx6xx10+4xx12xx20+7xx21xx35}{1xx5xx7+2xx10xx14+4xx20xx28+7xx35xx49}`
`=frac\{1xx3xx5+1xx2xx3xx2xx5xx2+1xx4xx3xx4xx5xx4+1xx7xx3xx7xx5xx7}{1xx5xx7+1xx2xx5xx2xx7xx2+1xx4xx5xx4xx7xx4+1xx7xx5xx7xx7xx7}`
`=frac\{1xx3xx5xx(1+2xx2xx2xx2+4xx4xx4+7xx7xx7)}{1xx5xx7xx(1+2xx2xx2+4xx4xx4+7xx7xx7)}=3/7`
Từ kết quả trên, ta có :
`3/7=303/707>303/708`
Vậy `frac\{1xx3xx5+2xx6xx10+4xx12xx20+7xx21xx35}{1xx5xx7+2xx10xx14+4xx20xx28+7xx35xx49}>303/708`