SOLUTION: What is the exact area of a circle with a diameter of 15 inches I think it would be {{{15pi}}} square inches?

No that's the circumference, the distance around the circle,
not the area, which is the amount of space inside the circle:
You found  inches, though the circumference 
would be in inches, not square inches

You don't want the circumference, you want the area, which is
found by the formula 

To find the area, we need the radius, not the diameter.
The radius is  of the diameter.

So the radius is  or 

Substituting  for  in the formula for the area of a circle:

 


 square inches or about 176.7 square inches.

Edwin