Why is a fixed interest rate almost always better than a variable interest rate?

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?

The random variable x is defined as the number marking the sector in which the arrow lands when the spinner in the diagram is spun once.