When you ask, can I take it that you don't understand the concept of quartile?

Understand the meaning of the topic first. Write again.

Quarter distance, IQR), also known as quartile deviation. It is a method to describe the difference between the third quartile and the first quartile in statistics (that is, the difference of Q 1~Q3). Like variance and standard deviation, it represents the deviation of variables in statistical data. Formula: IQR = Q3? Q 1

The lower quartile q1= x {[a]+1}+(a-[a]) (x {[a]+2}-x {[a]+1})

The upper quartile Q3 = x {[b]+1}+(b-[b]) (x {[b]+2}-x {[b]+1})

So the Q 1=6, Q2= 15 and Q3=26 of your question.

So we can calculate the distance between four o'clock =26-6=20.