init chapter-3
Update chapter-3.md
add images
Update chapter-3.md
add images
Update chapter-3.md
add images
Update chapter-3.md
add image
Update chapter-3.md
add images
Update chapter-3.md
add images and codes
Update chapter-3.md
add images
Update chapter-3.md
add images
Update chapter-3.md
Update chapter-3.md
add images