In order to find the value of x, let's solve this expression isolating the variable x:
[tex]\begin{gathered} \frac{6}{7}=\frac{91}{x} \\ \\ 6\cdot x=7\cdot91 \\ x=\frac{7\cdot91}{6} \\ x=106.17 \end{gathered}[/tex]So the value of x to make the fractions equivalent is x = 106.17.