[tex]\huge\boxed{25\%}[/tex]
We need to find the number of students that study art first. This includes the students who study both art and biology (4) and the students who study art but not biology.
We know the counts for every category except for "art but not biology", so we can use subtraction.
[tex]26-4-5-5=12[/tex]
This means that 12 students study art but not biology, which combines with the 4 who study both subjects to give us 16 art-studying students.
Now, we just need to find the probability that a student studies both subjects (4 students) given that they study art (16 students).
This is simple division.
[tex]4/16=0.25=25\%[/tex]
