Aria recorded the grade-level and instrument of everyone in the middle school School of Rock below.
Seventh Grade Students
Instrument # of Students
Guitar 13
Bass 9
Drums 3
Keyboard 6
Eighth Grade Students
Instrument # of Students
Guitar 14
Bass 15
Drums 6
Keyboard 5
Based on these results, express the probability that an eighth grader chosen at random will play an instrument other than bass as a fraction in simplest form.
The total number of eighth grade students who play an instrument is 14 + 15 + 6 + 5 = 40.
The number of eighth graders who play an instrument other than bass is 14 + 6 + 5 = 25.
Therefore, the probability that an eighth grader chosen at random will play an instrument other than bass is 25/40, which simplifies to 5/8.
Answer: $\boxed{\frac{5}{8}}$