ruby, 66 bytes

Result

WA

Duration

498ms

Code [DL]

require'matrix' p Matrix[*$<.map{|l|[6,*l.split.map(&:to_i)]}].det

stdin

28 12 20
82 35 80
08 50 52
07 37 68

stdout

stderr

/volume/CODE:1: syntax error, unexpected tIDENTIFIER, expecting end-of-input
require'matrix' p Matrix[*$<.map{|l|[6,*l.spli...
                ^

strace