Multiplying/dividing with exponents

I am having difficulties figuring out what exactly the author of my Algebra book is doing in regards to step 2.

Expression

$\displaystyle (\frac{x^3}{y^2}^5) (\frac{x}{y})^{-2}$

Step 1= $\displaystyle \frac{x^{15}}{y^{10}} * \frac{y^2}{x^2} $

Step 2= $\displaystyle x^{15-2} y^{2-10} $

Could some one please clearly explain whats going on from step 1 to step 2. When the expression turns into $\displaystyle x^{15-2} y^{2-10}$ is where im the most confused, if someone would please explain this transition that would be greatly appreciated. Unless the author is using $\displaystyle \frac{a^m}{a^n}=a^{n*m}$ to combine BOTH fractions.

Thanks!