At which age did A Lamusi participate in 2012 Summer?
2012 Summer refers to games_name = '2012 Summer';
SELECT T2.age FROM games AS T1 INNER JOIN games_competitor AS T2 ON T1.id = T2.games_id INNER JOIN person AS T3 ON T2.person_id = T3.id WHERE T1.games_name = '2012 Summer' AND T3.full_name = 'A Lamusi'