What is the standard deviation of this data?

Which of the fallowing best completes the sequence 12,8,5, a) 1 b) 2 c)4 d)0

You paint a 1/2 of a wall in 1/4 hour. how long will it take you to paint one wall

Jackie purchased 3 bottles of water and 2 cups of coffee for the family for $7.35. ryan bought 4 bottles of water and 1 cup of coffee for his family for 7.15. how much does each bottle of water cost? how much does each cup of coffee cost?