python3, 131 bytes

Result

WA

Duration

517ms

Code [DL]

s=map(int,open(0).read().split())
a,b,c,d,e,f,g,h,i=[s[i+3]-s[i%3]for i in range(9)]
print((a*(e*i-h*f)+b*(f*g-i*d)+c*(d*h-g*e))/6)

stdin

66 50 24
13 41 09
91 20 83
96 71 84

stdout

stderr

Traceback (most recent call last):
  File "/volume/CODE", line 2, in <module>
    a,b,c,d,e,f,g,h,i=[s[i+3]-s[i%3]for i in range(9)]
  File "/volume/CODE", line 2, in <listcomp>
    a,b,c,d,e,f,g,h,i=[s[i+3]-s[i%3]for i in range(9)]
TypeError: 'map' object is not subscriptable

strace