am in a 3d coordinate system;
I got the points
0(0,0,0)
C(0,6,0)
F(0,0,3)
P(x,6,0)
together these points form a pyramid. The given volume for the pyramid is 9 VU (volume units).
V = 1/3 * Ag * h
V = 9, h = length of F = 3 LU (Length units)
9 = 1/3 Ag * 3
9 = Ag
line 0C and CP form a right angle, so Ag is 1/2 * a * b
9 = 1/2 a * b
for b i set length of 0C = 6 LE
9 = 1/2 * a * 6
3 = a
now with length of a line: 3 = sqrt( (x-0)^2 + (6-6)^2 + (0-0)^2 )
9 = x^2
x = +/- 3