What is the square root of –16?

I've never been good at math he told he loves but he keeps cheating on me, so it ain't adding up sis

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?

What is the solution set of the quadratic inequality x^2-5< or equal to 0