An alien invades Earth.  It abducts 200 people.  He returns 80% of the people abducted.  After that he takes 10 people to another planet.  He took the rest to his home planet.  How many people did he take to his home planet?
He returned 200*.8=<<200*.8=160>>160 people
So he had 200-160=<<200-160=40>>40 people
He took 10 of those to another planet so he took 40-10=<<30=30>>30 to his home planet
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