Gary and Linda are at the movies. Gary has $9 to spend on snacks and Linda has $10 to spend on snacks. Gary buys nachos. Linda does not buy any snacks at the movies. If linda has $4.55 more than gary after he buys nachos, how much did gary pay for the nachos?
Gary started with $9
Linda started with $10
After Gary buys nachos, he has $5.45 (4.55 less than Linda's 10.00)
So, the nachos cost $3.55 (9.00 less the 5.45 he has left)
Or, you can reason that Linda started out with $1.00 more than Gary.
She ended up with $4.55 more, so Gary must have lost $3.55.