The base of a cone is a circle.
The area of a circle is

.
Thus, the area of the base of a cone

.
The derivation of the formula for the area of a circle involves a bit of calculus, but if you'd like, I can walk you through it.
Your answer is d.14,230.0in^3
The answer to your math question is 66°.
Adding 47° and 67° is 114°.
Subtracting 114° from 180° equals 66°.
A. x = -6
6-x-x = 18
6-2x =18
-2x = 12
x = -6