The question is incomplete. But it is about the method which is an example of problem solving strategy that Peter is using to find Teddy.
The answer is peter is Peter is using the method which is called algorithm in problem solving strategy.
The complete question is;
Peter is playing hide and seek with his 6 yr old nephew, Teddy. Peter decides to look around the house room by room and then shuts the each door when he has finished looking in each room. The method Peter is using to find Teddy is an example of which problem-solving strategy?