William bought a new sweater at the store when they were having a %45 off sale.
if the regular price of the sweater was $19 how much did william pay with the discount?

How do you solve a question like this?

You give a $4 tip for a meal that cost $22. approximately what percent of the bill was your tip?

In a fruit survey, 300 children choose their favorite fruit out of apples, bananas, and watermelon. 150 chose apples and 90 chose bananas. what percent chose watermelon?