So since the book has 8 chapters we will say that this book has 8 sections. This meaning each chapter is 1/8th of the entire book. So if you read 4 chapters then this will give you a fraction of 4/8th which can be simplified to 1/2. Since you’ve read 1/2 of the book that means Mary has 1/2 of the book left to read. Hope this helps.
