There were w dollars in Olivia's wallet. She collected x more dollars from an atm. After she visited a supermarket there were y dollars left. How much more money did she spend at the supermarket than she collected at the atm?
First, we need to find out how much money Olivia had in total. We know that she had w dollars in her wallet to start with, and she collected x more dollars from the ATM. This means that she had w + x dollars in total. 

Now, we need to find out how much money she spent at the supermarket. We know that she had y dollars left after she visited the supermarket. This means that she must have spent (w + x - y) dollars at the supermarket. 

Therefore, the answer (symbolic expression) is: 

w + x - y