If $$\log_x\left(\frac57\right)=\frac{-1}3$$, then the value of x is

Operators $$\square$$,◊,$$\rightarrow$$ are defined by : a $$\square$$ b = $$\frac{a-b}{a+b}$$; a ◊ b = $$\frac{a+b}{a-b}$$; a $$\rightarrow$$ b = ab. Find the value of (66 $$\square$$ 6) $$\rightarrow$$ (66 ◊ 6).