The author of some young adult books wants to know more about the kinds of books his reader prefers. Which of the following describes the best sampling of readers for the author to use in a survey? 5,000 young adults who visit the mall on a particular day

5,000 librarians who are registered to a national librarians organization

5,000 customers who have just purchased ebooks from a website

5,000 middle school students in his city

a=24; b=12

step-by-step explanation:

a/b=2: 1

a=2b

36/(1+2)=12

b=12

a=24

step-by-step explanation: given equation a = h(b 1+b 2)

also we are given values of a, h and b 1 as :

a = 16, h = 4, and b 1 = 3.

in order to solve it for b 2, we need to plug the given values of   a, h and b 1 .

therefore, plugging values of   a, h and b 1   in given equation, we get

16 = 4( 3 + b 2)

first dividing both sides by 4, we get

4 = 3 + b 2

subtracting 3 from both sides, we get

4 -3 = 3 -3 + b 2

1 = b 2.