As Bart says meaning of this sentence is "7 out of 10 people will have a flying car." "on kişiden yedisinin" means "7 out of 10 people" On kişiden yedisinin - ON(10) KİŞİ(person) -DEN(from,through but in this sentence it means 'out of' -den can be mean a lot of things but I just wrote common ones.) YEDİ(7) -SİNİN(to have)

7 out of 10 people will have a flying car.

سبعة اشخاص من مجموع عشرة