Help:( If you were to solve the following system by substitution, what would be the best variable to solve for and from what equation?
21+ =9
31-121= 15
A. x; in the first equation
B. Xin the first equation
c. x in the second equation
D. , in the second equation

List the elements of the set in roster notation. (enter empty or ∅ for the empty set.) {x | x is a letter in the word hippopotamus}

Convert 50 kilogram to pounds. (the conversion factor from kilogram to pound is 2.2046.) a. 52.2 lb. b. 110.2 lb. c. 22.6 lb. d. 47.8 lb.

Which situation can be modeled by the inequality 5 + 10w ≥ 45? a. you start with $5 and save $10 a week until you have at least $45. b. you start with 5 baseball cards and purchase 10 cards every week until you have at most 45 cards. c. you start with 5 water bottles and purchases cases of 10 water bottles each until you have a total of 45 water bottles. d. you spend $5 plus $10 per week until you have less than $45.