Answer:
The third quartile, Q3, is the same as the 75th percentile.
75% of data will be less than 75th percentile; 25% of data will be more than 75th percentile
The interquartile range of a set of scores is the difference between the third and first quartile - that is, the difference between the 75th and 25th percentiles. The 75th percentile is between 78 and 86, so, if 41 is subtracted from those numbers, the upper and lower bounds of the 25th percentile can be found.
