VTMO 2026 - Grade 8 - Semifinal - SET 04 - Self-study Question 20

Start with the set $\{1,2,3,4,5,6,7\}$. At each step choose two numbers, subtract $1$ from one and add $5$ to the other. After some steps the resulting set is $\{2012,2013,2014,2015,2016,2017,x\}$. Which listed value is $x$?