It takes 12 + 9 =<<12+9=21>>21 minutes to bake each cake.
It takes 21 + 6 = <<21+6=27>>27 minutes to cool and decorate each cake.
Therefore, it takes a total of 12 + 21 + 27 = <<12+21+27=60>>60 minutes to make one cake.
Thus, it takes 60/60 = <<60/60=1>>1 hour to bake one cake.
So, it will take 1 x 6 = <<6=6>>6 hours to bake all 6 cakes.
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