How to i solve this Exponential equation How to solve this exponential equation? 
$$7 \cdot 3^{x+1} - 5^{x+2}= 3^{x+4}- 5^{x+3}$$

$$7 \cdot 3^{x+1} - 5^{x+2}= 3^{x+4}- 5^{x+3}$$
$$21 \cdot 3^{x} -25\cdot 5^{x}= 81\cdot3^{x}- 125\cdot5^{x}$$
$$100\cdot 5^{x}= 60\cdot3^{x}$$
$$\left(\frac{5}{3}\right)^x=\frac{3}{5}=\left(\frac{5}{3}\right)^{-1}$$
$$x=-1$$
