Hey can someone help me I dont really undertstand this, (thank you ^^)

Answer:
exact area = 81π in.²
approximate area = 254.34 in.²
Step-by-step explanation:
Exact:
area = πr²
r = radius = diameter/2 = 18 in./2 = 9 in.
area = πr²
area = π × (9 in.)²
area = 81π in.²
exact area = 81π in.²
Approximate:
π = 3.14 (approximately)
area = πr²
area = 81π in²
area = 81 × 3.14 in.²
approximate area = 254.34 in.²