Add 2.7 and 2.8 from the most recent version of the book

[iamhectorotero]

Exercises missing

Two new exercises (2.7 and 2.8) appear in the latest version of the book available online and they don't in the repository.

Check the book online for the exercises and add statements and solutions.

[HaleTom]

Answers are given here:
https://yashbonde.github.io/blogs/bartosutton/chap2_ex.html

[iamhectorotero]

Hi @HaleTom, thanks for your comment! The idea would be to add the statements and solutions to this repository :)