Here's what we know:
Acir = πr2 (Area of a circle equals pi times the radius squared)
π = 3.14
r = 1/2 * 8 = 4 (The radius is half of the diameter (which is 8 inches), so it equals 4 in.)
That leaves us with:
A = 3.14 * 42
You should be able to solve from here.