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[5]*l[6]-l[3]*l[8])+l[9]*(l[4]*l[8]-l[7]*l[5]))/6) ZZ