The area of the right triangle =

b = base = SV = 12.3
h = hight = HL = 24.6
A = area

Answer:

Step-by-step explanation:
The base of the pyramid we need to study is a hexagon.
Let's look at the attached image of an hexagon to understand how we are going to find the area of this figure.
Notice that an hexagon is the combination of 6 exactly equal equilateral triangles in our case of size "2x" (notice that the "radius" of the hexagon is given as "2x")
Therefore the area of the hexagon is going to be 6 times the area of one of those equilateral triangles.
We know the area of a triangle is the product of its base times its height, divided by 2: 
We notice that the triangle's height is exactly what is called the "apothem" of the hexagon (depicted in green in our figure) which measures
, so replacing this value in the formula above for the area of one of the triangles:

Then we multiply this area times 6 to get the total area of the hexagon (6 of these triangles):
Area of hexagon = 
which is the last option given in the list.
1/2d+6=1/2(d+12)
Leaving us with 0.5 or 1/2
I'm may not be that good at math, but I'm going to try my best to help you, because I know how it feels to be in this situation!
The first one :
You might be right on D. But I'm thinking B also. The question asks "Which could be a cross section of a rectangular pyramid that has been intersected by a plane perpendicular". But a triangle is basically a flat pyramid.
(I'm typing really fast to help!!!!)
Second one: Its B!! Look at it really closely! You'll get it!!!
(Going really fast now!!!!)
Third one: Between B or D!!! But I think you're right on your choice!!!!
(FASTER FASTER!!!)
FINALLY: Copy and paste your answers into google. People have asked the same question!
I hope I helped. I don't want to make you fail, as I am in the SAME similar situation as you! I really REALLY REALLY HOPE YOU PASS!!!