13 : 14
$latex \frac{x}{y} = \frac{3}{1}&s=1$
$latex => \frac{x^{3}}{y^{3}} = \frac{27}{1}&s=1$
$latex => \frac{x^{3}-y^{3}}{x^{3}+y^{3}}=\frac{27-1}{27+1}= \frac{26}{28}&s=1$
$latex => \frac{26}{28}= \frac{13}{14} = 13 : 14&s=1$
Hence option [B] is the right answer.