Revert "added lesson 3"

This reverts commit 223b62f64df4d036fbb7afc71fa6d6ec4ba2cab0.
Revert "Revert "added lesson 3""

This reverts commit 182df95444596063ed4ff51ee1a36059d82cbae5.
Revert "Revert "Revert "added lesson 3"""

This reverts commit 116480dae6570eae6b0dff4176689f1546c29ca6.
Revert "Revert "Revert "Revert "added lesson 3""""

This reverts commit 2c196ada71facf4a8490f3fa48cfd725b8375d6a.
Revert "Revert "Revert "Revert "Revert "added lesson 3"""""

This reverts commit fd893d890c9a8bc9c88c208da17c170e24a2dbaf.