Statement 1: Inscribed in a semicircle means the angle facing opposite the diameter is 90 degree. Area = 1/2*b*h. b =20. h or height we don't know. h will be different if the triangle is 90-45-45, or 90-30-60. Hence Insufficient
Statement 2: Says its isosceles, but no other detail. no angles, no base or height data. Hence Insufficient.
together we know the triangle is 90-45-45, with base 20. Hence area can be calculated. Sufficient. Ans is C
The angle opposite to the Diameter(i.e., hypotenuse) is 90, so if we draw a line from the mid point of the diameter(point will be center of the circle) to the vertex that is making 90 degrees then it becomes the height(altitude).
So we can calculate the area of the traingle by (1/2)*height*hypotenuse.
So A is sufficient to calculate and i ended up here.
Please correct me if i am missing something here. thanks.