All that you need to solve this task is to use basic Z-statistic approach
Start like that \(P(X(BAR) \ \textgreater \ 17)\)
Then you have \(Z = X(BAR) - 15 / (6.4/sqrt(30))\)
And to complete the task you need to caclulate that with standard table
\(P(Z\ \textgreater \ (17-15)/(6.4/sqrt(30))\)