pls explain.thanks

(8 points) A fair, 8-sided die is rolled 18 times. What is the expected sum of the numbers that come up on the 18 rolls? Enter your answer as a whole number or a decimal. Hint: Suppose the question said that a fair, 6-sided die was rolled 7 times, and asked for the expected value of the sum of the 7 rolls. The expected value of the number on a single roll would be the ordinary average of the numbers 1. 2, 3, 4, 5, and 6 - the 'ordinary' average because each value is equally likely - so it is (1 + 2 + 3 + 4+5+ 6) /6 = 3.5. Since the expected value of each roll is 3.5, the expected value of the sum of the 7 rolls is 3.5 + 3.5 + 3.5 + 3.5+ 3.5 + 3.5 + 3.5 = 7 * 3.5 = 24.5