ta có :13/15=13.111/15.111=1433/1665
có :1-1443/1665=222/1665;1-1333/1555=222/1555
mà:222/1665<222/1555=>1-1443/1665<1-1333/1555
=>1443/1665>1333/1555
=>13/15>1333/1555
\(\frac{1333}{1555}\)= \(\frac{13}{15}\)nên \(\frac{13}{15}\)=\(\frac{1333}{1555}\)