If the ratio of fast readers to slow readers is 9 to 5,
and there 4,716 fast readers, how many slow readers are
there? ( show your work )

W is to X as Y is to Z

can be written in equation form as

W/X = Y/Z 

Your problem essentially says 

NUMBER OF FAST READERS is to NUMBER OF SLOW READERS as
9 is to 5.

Let x = the number of slow readers, then since the number
of fast readers is given as 4716, we can say

4716 is to x as 9 is to 5

which can be written as this equation:

4716/x = 9/5

Multiply both sides by LCD = 5x, or what amounts to the
same thing, cross-multiply, and get

23580 = 9x

x = 23580/9

x = 2620

Edwin
AnlytcPhil@aol.com