Mai used 4000 dong to buy a comic book. She used half of the remaining money to buy a magazine. Lastly, she used 1000 dong more than half of the remaining money to buy a pen. She was left with 5000 dong. How much money had Mai at first

Mai used 4000 dong to buy a comic book . She used half of the remaining money to buy a magzine . LAstly , she used 1000 dong more than half of the remaining money to buy a pen . She was left with 5000 dong . How much money had Mai at first?
Mình rất rất là cảm ơn bạn nào giải giùm mình được bài này!!!Mong các bạn sớm thấy và làm nhanh giùm mình nha.Vì 5:35 là mình đi học òi!!! Iu các bạn rứt rứt nhìu :)))))