Standard deviation for 20,13,5,8,10

Will give brainliest sum of arithmetic series (sigma notation) find the numerical answer to the summation given below. (image shown below)

What kinds of numbers make up the set of numbers called the real numbers? give examples when you explain a number type. there are a limited set of types of numbers, but an unlimited number of examples of these numbers.

Car a and car b were in a race .the driver of car b claimed that his car was twice as fast as car a