Answer:
5
Step-by-step explanation:
You are looking for x so what you are really looking for is what times 4 =20 and that is 5.
5x4=20
25/5 5
10/5 2
5/2 is 25/10 but in simplest form
Check the picture below.
notice the midpoint of the diameter segment, is just 1,9.
also, recall the radius is half the diameter, notice how long the radius is, just 4 units.