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?
##Solution## 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
#### 30