vim, 198 bytes

Result

WA

Duration

542ms

Code [DL]

VGJ:let l=map(split(getline(1),' '),'str2nr')
:for i in range(9)
let l[i+3]-=l[i%3]
endfor
:call setline(1, (l[11]*(l[7]*l[3]-l[4]*l[6])+l[10]*(l[3]*l[8]-l[5]*l[6])+l[9]*(l[4]*l[8]-l[7]*l[5]))/6)
ZZ

Disassembly

VGJ:let l=map(split(getline(1),' '),'str2nr')<NL>:for i in range(9)<NL>let l[i+3]-=l[i%3]<NL>endfor<NL>:call setline(1, (l[11]*(l[7]*l[3]-l[4]*l[6])+l[10]*(l[3]*l[8]-l[5]*l[6])+l[9]*(l[4]*l[8]-l[7]*l[5]))/6)<NL>ZZ

stdin

06 52 02
32 21 04
68 63 20
19 56 85

stdout

29516

stderr

strace