How many strings of eight uppercase english letters are there if no letter can be repeated?

Out of the 180 students at a summer camp, 72 signed up for canoeing. there were 23 students who signed up for trekking, and 13 of those students also signed up for canoeing. use a two-way table to organize the information and answer the following question: approximately what percentage of students signed up for neither canoeing nor trekking? 72% 40% 54% 98%