This is the first section.
It is 3/12 width (and left) on desktop and tablet, and 100% width on phone.
This is the second section.
It is 6/12 width on desktop (and central), 9/12 width on tablet (and right), and 100% width on phone.
This is the third section.
It is 3/12 width on desktop (and right)) and 100% width on tablet and phone.