stuck, 167 bytes

Result

AC

Duration

503ms

Code [DL]

ssss["x:map(int,x.split())"m["x:[x[i/3+1][i%3]-x[0][i%3] for i in range(9)]"m"x:(x[1]*(x[5]*x[6]-x[3]*x[8])+x[2]*(x[3]*x[7]-x[4]*x[6])+x[0]*(x[4]*x[8]-x[5]*x[7]))/6"m]

stdin

31 96 94
29 08 89
57 64 19
79 60 14

stdout

21840

stderr

strace