How do you know if an equation is linear or not?

Find the average speed of a rabbit that runs a distance of 22 m in a time of 1.8 s .

Clara schumann is buying bagels for her coworkers, she buys a dozen bagels priced at $5.49 a dozen. the bakery's cost for making the bagels is $2.25 per dozen. what is the markup rate based on selling price on a dozen bagels?

If you have 12 feet of string and you cut it into equal length of 5 inches each how much string will be left