The interquartile range (IQR) is found by subtracting Q1 from Q3.
First, find the median.
10, 12, 28, 59, 61, 67, 89, 93
12, 28, 59, 61, 67, 89
28, 59, 61, 67
59, 61
median = 60
Second, separate the data set at the median and find the median of each of those sections (do not include the median number we just found).
data set one = 10, 12, 28, 59
median of data set one = 20 (a.k.a. Q1)
data set two = 61, 67, 89, 93
median of data set two = 78 (a.k.a. Q3)
Third, subtract Q1 from Q3 to get the IQR.
Q3 - Q1 = IQR
78 - 20 = 58
Answer: 58
Hope this helps!