Algebra-1

Question Analysis
This question tests the student's ability to find the upper quartile (Q3) of a given data set. The data must be sorted in ascending order, and Q3 is the median of the second half of the data.

Key Concept Explanation
Q3 (Upper Quartile) is the value at the 3/4 position in a sorted data set. It divides the data into four equal parts, with 75% of the data below it.

Step-by-step Solution
1. Sort the data in ascending order: 18, 20, 21, 2...