Brian read two books with 15 chapters, so he read 2*15=<<2*15=30>>30 chapters.

He also read a book with 20 chapters, bringing the total for the first three to 30+20=<<30+20=50>>50 chapters.

He then read a book with half the chapters of his cumulative total so far, so it had 50/2=<<50/2=25>>25 chapters

In total, he read 30+20+25=<<30+20+25=75>>75 chapters.

# Answer

75
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Brian likes to read books.  He read one book that had 20 chapters, two books that had 15 chapters each, and one book that had half the chapters of the three previous books put together. How many chapters of books did Brian read?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
75
Brian likes to read books.  He read one book that had 20 chapters, two books that had 15 chapters each, and one book that had half the chapters of the three previous books put together. How many chapters of books did Brian read?
train