csharp, 349 bytes

Result

WA

Duration

887ms

Code [DL]

using System;
using System.Linq;
class A{static void Main(){
string s="";
for(int i=4;i>0;i--){
  s+=Console.ReadLine()+" ";
}
int[] a=s.Split(' ').Take(12).Select(Int32.Parse).ToArray();
foreach(int z in Enumerable.Range(0,8)){a[z]-=a[9+z%3];}
Console.Write(-(a[7]*(a[3]*a[2]-a[0]*a[5])+a[6]*(a[1]*a[5]-a[4]*a[2])+a[8]*(a[0]*a[4]-a[3]*a[1]))/6);
}}

stdin

87 42 13
15 30 23
03 80 89
18 51 02

stdout

29162

stderr

strace