If ( 3/5 )^3 ( 3/5 )^ - 6 = ( 3/5 )^2x - 1 then x is equal to ?

Answer: Option B

$$\begin{array}{rl}& {\left(\frac{3}{5}\right)}^3{\left(\frac{3}{5}\right)}^{-6}={\left(\frac{3}{5}\right)}^{2x-1}\\ & \Rightarrow {\left(\frac{3}{5}\right)}^{\left(3-6\right)}={\left(\frac{3}{5}\right)}^{2x-1}\\ & \Rightarrow {\left(\frac{3}{5}\right)}^{-3}={\left(\frac{3}{5}\right)}^{2x-1}\\ & \Rightarrow 2x-1=-3\\ & \Rightarrow 2x=-2\\ & \Rightarrow x=-1\end{array}$$