The HCF of $\frac{3}{4},\frac{7}{8}$ and $\frac{13}{14}$ is:

$\frac{1}{56}$

HCF of fraction = \(\frac{HCF\;of\;numerator}{LCM\; of\;denominator}\)

The given fractions are :  $\frac{3}{4},\frac{7}{8}$ and $\frac{13}{14}$.

LCM of 4, 8, 14 = 56

HCF of 3, 7, 13= 1

The HCF of $\frac{3}{4},\frac{7}{8}$ and $\frac{13}{14}$. is = \(\frac{1}{56}\)