is it that you need help to understand this? If so
So first of all you can see that outside the bracket there's a power 3. You will need to use the power 3 and multiply everything in the bracket. so at step 1 you see that the power 3 is gone. Next, as you can see in the bracket,the lower part of the fraction has a dot in the middle and that's multiply. so you take y multiply with y and x multiply with x. and that is how step 2 is formed. Then, if it's a fraction then it means divide. the upper part is divided by the power part. and divide means minus here so you take the x^-12-36 so that forms x^-48. and you do the same with y.
hope you understand what I was explaining I tried my best