Remember to combine like terms, aka whichever number has the same variable (or no variable), those are the ones that go together. 5 + 10 is 15. -3i + 5i is the same as 5i -3i, which is 2i.
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?