Need help solving the quant problems

GRE Quant Problem Solving
1

I am following gregs 1 month study plan. Which book is he following for exercises in the videos.

2

Missing context.

3

which book is he following in the videos for quant

4

Either the Big Book or one of the official ETS GRE books (I think he tells the source in many of the problems, or you can look up the problems directly on the internet).