Kris forwards an e-mail to 5 people. each of those people forward that e-mail to 5 more people. if this happens two more times, which expression shows the total number of people who have received the e-mail, not including kris?

Kris forwards an e-mail to 5 people. Each of those people forward that e-mail to 5 more people. ( 5 * 5 )
If this happens two more times ( 5 * 5 * 5 * 5 )

the expression for this would be 5^4, or five to the fourth power

5 * 5 * 5 * 5 = 625
5^4 = 625

Y= 5^x
Im actually not sure, thats just a guess.