Answer: The council should survey 11 Democrats.
Explanation:
A proportional relationship is written as:
y = k*x
Where k is the constant of proportionality. y is the number of surveyed members, and x is the total number of registered members.
If we use the same proportion for each case, then we will use the same value of k.
We know that there are 20553 registered Republicans, and the council decides to survey 13 of them, then we will have the relation:
13 = k*20553
Now we can solve this for k:
13/20553 = k
Then the proportional relationship will be:
y = (13/20553)*x
The number of democrats they should survey can be found if we replace x by the number of registered Democrats, then we use x = 17391
this leads to:
y = (13/20553)*17391 = 11
The company should survey 11 Democrats.