Answer:
The length of BC is 17
Step-by-step explanation:
When we construct a triangle with the data, we will end up a isosceles triangle.
In a isosceles triangle , we know that tow angles and two sides are equal
The questions states that

Then sides AC and AB are also equal
On equation their values
2X - 8 = X+9
2X = X + 9 +8
2X = X + 17
2X - X = 17
X = 17
The length of BC = X = 17
The mean is <span>29.25 but you need to round it so it would be 30 hope it helps <3</span>
You have to split it into triangles
but you have to know how to use pythagorus in 3D shapes
I thinks it C, this a difficult question but idk, that my closest guess...