In chapter 7, [exercise 5](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_5/) is a duplicate of [exercise 4](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_4/). same goes for the following exercises: [7](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_7/) and [8](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_8/). [12](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_12/) and [13](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_12/). [18](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_18/) and [19](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_18/). [25](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_25/) and [26](https://aimacode.github.io/aima-exercises/knowledge-logic-exercises/ex_2/).
