Each table takes 12 pieces of wood to make so 24 tables will take 24*12 = <<12*24=288>>288
There were originally 672 pieces of wood so now there are 672-288 = <<672-288=384>>384 pieces left
8 pieces of wood make 1 chair so 384 pieces can make 384/8 = <<384/8=48>>48 chairs
#### 48