200 * 2/15 = the number of students that didn't read any books. This is 26.6, so 40 is not a good estimate 40 students is 20 percent versus 26 being approximately 13 percent.
Jeremy did not make a good inference. The ratio is not in proportion to 2/15. The correct inference would be about 26 students who did not read any books in July. The sample might be biased since it was limited to those at the pool.