The table above shows the number of students in Grade 9 and Grade 10 who joined a sports club or an art club. There are 30 students in total. If a student is selected at random, the probability that the student is a Grade 10 student who joined the Art Club is . What is the value of x?
| Grade Level | Joined Sports Club | Joined Art Club | Total |
|---|---|---|---|
| Grade 9 | 10 | 5 | 15 |
| Grade 10 | 8 | x | |
| Total | 30 |
