There were 41 dollars in Olivia's wallet. She collected 42 more dollars from an atm. After she visited a supermarket there were 25 dollars left. How much more money did she spend at the supermarket than she collected at the atm?
Olivia had 41 dollars in her wallet. 
She collected 42 more dollars from the ATM, so now she has 41 + 42 = 83 dollars. 
She visited the supermarket and spent some money, so now she has 83 - 25 = 58 dollars left. 

We want to know how much money she spent at the supermarket, which is the same as asking how much money she had before visiting the supermarket (83 dollars) minus how much money she has now (58 dollars). So she spent 83 - 58 = 25 dollars at the supermarket.