Question

Students in a geography class were taking a poll to see what international destinations had been visited by members of the 34 person class. It was determined that 7 had never left the US, 15 had gone to India, 18 have gone to Poland and 11 have gone to Trinidad and Tobago. Upon further inspection, it was determined that 13 students had been to exactly 2 countries, 2 had been to all 3 of the countries mentioned, 11 have been to India and Poland and 26 have been to at least one of Poland and Trinidad and Tobago. How many students have been to Poland and Trinidad and Tobago, but not to India.