Answer:
18, 15, 11, 14, 19, 15, 6
Explanation:
1. 7,7,11,14,16,16,17 : 14 is the median
2. 6,9,13,16,18,19,20 : 16 is the median
3. 8,9,12,13,15,16,17 : 13 is the median
it's basically the middle number of the pattern once you put in in order from least to greatest or greatest to least .