kotlin, 237 bytes

Result

TLE

Code [DL]

fun main(args:Array<String>){
val a=(0..3).flatMap{_->readLine()!!.split(" ").map{a->a.toInt()}}.toMutableList()
for(z in 0..8)a[z]-=a[9+z%3]
println((a[7]*(a[0]*a[5]-a[3]*a[2])+a[6]*(a[4]*a[2]-a[1]*a[5])+a[8]*(a[3]*a[1]-a[0]*a[4]))/6)
}

stdin

29 59 71
92 05 08
80 86 09
53 37 67

stdout

stderr

strace