How many variable terms are in the expression 3x3y + 5xz − 4y + x − z + 9? (input a numeric value only.)

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?