There were 36 dollars in Olivia's wallet. She collected 21 more dollars from an atm. After she visited a supermarket there were 4 dollars left. How much more money did she spend at the supermarket than she collected at the atm?
Olivia had 36 dollars in her wallet. 
She collected 21 more dollars from an ATM. 
That means she had a total of 57 dollars. 
After she visited the supermarket, she had 4 dollars left. 
That means she spent 53 dollars at the supermarket. 

The difference between what she spent at the supermarket and what she collected from the ATM is 53 - 57, which is -4.