A: Hello,what are you doing?

B:I am watching a film.

A: what is its name?

B:Its name Harry Potter. It's a good film. I like it.

A: I like it too. It's about a witch boy who name Harry Potter, isn't it?

B: Yes, he fight with some bad witchs but they have a strong magic.

A: And he win, isn't it?

B: Great, do you want to watch this film with me?

A: Sure!

a) 5 . 3^x = 405

3^x = 405 : 5

3^x = 81

3^x = 3⁴

=> x=4

b) -81 - x = -113

x = -113 - (-81)

x = -113 + 81

x = -32

thanks các bạn nha