Well you never sent a picture but the most logical answer is 80 cm
Remark
The number of faces reaching out in the 3rd dimension of the pyramid = the number of edges on the base.
Givens
Number of edges (or sides on the base)= e
Number of faces = f
Formula
F = e + 1 Don't forget that the base is also a face.
You should get photo math you can take a picture and it will give you the answer and show you how to solve it
Answer:
AC+ CD = ACD
X+1 + 2X + 2 = 30
3X+3 =30
3X=30–3
3X=27
X= 27/ 3
X= 9
I'm not sure of the solution, but I solved it according to a straight line (Line segment) .
I hope I helped you^_^