in a class of 100 students, 45 students read physics, 52 students read chemistry and 15 students read both physics and chemistry. find the number of students who study neither physics nor chemistry​

Aparticular telephone number is used to receive both voice calls and fax messages. suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls. (a) what is the expected number of calls among the 25 that involve a fax message?