<h2>
Answer:</h2>
The the number of students who sign up for all three clubs = 6
<h2>
Step-by-step explanation:</h2>
The total number of students in the class is given by:
Total number of students= Number of students in poetry club+Number of students in history club+Number of students in writing club-Number of students in exactly 2 clubs-2×Number of students in all the three clubs.
Based on the information we have:
Total number of students= 59
Number of students in poetry club= 22
Number of students in history club= 27
Number of students in writing club= 28
and number of students in exactly two clubs=6
Let the number of students in the three club= x
Hence, we have:
59=22+27+28-6-2x
i.e.
59=71-2x
i.e.
2x=71-59
i.e.
2x=12
i.e.
x=6
Hence, the answer is: 6
