Intersection of three planes

class Plane3D:
def equation_plane(x1, y1, z1, x2, y2, z2, x3, y3, z3):
a1 = x2 - x1
b1 = y2 - y1
c1 = z2 - z1
a2 = x3 - x1
b2 = y3 - y1
c2 = z3 - z1
a = b1 * c2 - b2 * c1
b = a2 * c1 - a1 * c2
c = a1 * b2 - b1 * a2
d = (- a * x1 - b * y1 - c * z1)
print ("The equation of the plane is "),
print (a, "x +" ,b, "y +" ,c, "z +" ,d, "= 0.")
print (a)
print(b)
print(c)
print(d)
return equation_plane(x1, y1, z1, x2, y2, z2, x3, y3, z3)

def cramers (self, p1, p2,p3):
from numpy import linalg
As=[[2,-1,5,1],[3,2,2,-6],[1,3,3,-1],[5,-2,-3,3]]
Bs=[-3,-32,-47,49]
Cs=[[2,-1,5,1],[3,2,2,-6],[1,3,3,-1],[5,-2,-3,3]]
Xs=[]
for i in range(0,len(B)):
for j in range(0,len(B)):
C[j][i]=B[j]
if i>0:
C[j][i-1]=A[j][i-1]
X.append(round(linalg.det(C)/linalg.det(A),1))
return (X)
That's where i am i don't know what to do next