To find out how many books Matt read, you can subtract the number of books he read from the number of books Rob read.
Rob read 71 books, and Matt read 36 fewer books:
\[ \text{Books read by Matt} = \text{Books read by Rob} - 36 \]
\[ \text{Books read by Matt} = 71 - 36 = 35 \]
So, Matt read 35 books.