How to round 9921 in to the nearest ten

Arefrigeration system at your company uses temperature sensors fixed to read celsius (°c) values, but the system operators in your control room understand only the fahrenheit scale. you have been asked to make a fahrenheit (°f) label for the high temperature alarm, which is set to ring whenever the system temperature rises above –10°c. what fahrenheit value should you write on the label

Atriangle with all sides of equal length is a/an triangle. a. right b. scalene c. equilateral d. isosceles

Factor the polynomial by its greatest common monomial factor.