We have to calculate the proportion (expressed in percentage) of students who do not play sports and play a musical instruments.
We can calculate this proportion as the quotient between the students who do not play sports and play a musical instruments (7 students) and the total numer of the students in the survey (we have to add all the categories):
[tex]p=\frac{7}{6+7+8+3}=\frac{7}{24}\approx0.2917\approx29\%[/tex]We can approximate this percentage to 30%.
Answer: 30%