The two box-and-whisker plots below show the scores on a math exam for two classes. what do the interquartile ranges tell you about the two classes?

The interquartile range is a measure that indicates the extent to which the central 50% of values within the data set are dispersed.
The interquartile range: Upper quartile - Lower quartile
As we can see in the box-and-whisker plots:
Class A:  89-66 = 23
Class B: 94-79 = 15
This shows that the spread in the scores of class A within the central 50% of values is higher than the spread of the scores of the class B.