I am continuously getting the error whenever trying to run the query
You only can create one view with the same name.
DROP VIEW IF EXISTS chinook.customer_gt_90_dollars CREATE .....
Next time, please include mission url links within your post. It will help the reader to understand the problem and answer them as quickly as possible.
Here is a reference on how you can help yourself to get a better response on your questions.
Type out the code in the post. Why? The reader can copy and paste the code and test it out rather than manually. Most importantly, it helps to think through what you have done and a better written post helps the reader to figure out what exactly the problem lies.