This is expected value am I right?
Try these links:
https://www.statisticshowto.datasciencecentral.com/probability-and-statistics/expected-value/
https://artofproblemsolving.com/wiki/index.php/Expected_value
https://artofproblemsolving.com/videos/counting/chapter11/122
Then post your answer, so I might confirm it.
Answer: 52/3...