Chapter 2 - Set Theory - 2.1 Basic Set Concepts - Exercise Set 2.1 - Page 59: 109

{Ireland, Switzerland, United Kingdom }

x is a country in which 8% $\leq$ percentage having used marijuana $\leq$ 12.3% From the graph Ireland = 8%, Switzerland = 8.5% United Kingdom = 9% So set = {Ireland, Switzerland, United Kingdom }