lua, 208 bytes

Result

WA

Duration

496ms

Code [DL]

a={}for k=1,4 do for s in string.gmatch(io.read(),"%w+")do a[#a+1]=s end end
for z=1,9 do a[z]=a[z]-a[10+~-z%3]end
print((a[8]*(a[1]*a[6]-a[4]*a[3])+a[7]*(a[5]*a[3]-a[2]*a[6])+a[9]*(a[4]*a[2]-a[1]*a[5]))%1/6)

stdin

15 86 08
49 40 97
05 63 64
99 26 49

stdout

0.0

stderr

strace