Find All Numbers X That Satisfy the Equation $\frac{\log _{6} 28 x}{\log _{6} 7 x}=2$

Find all numbers x that satisfy the equation $\frac{\log _{6} 28 x}{\log _{6} 7 x}=2$ .

A) 7
B) 4
C) 28
D) 0.57