Count the number of members in club "Bootup Baltimore" whose age is below 18.
SELECT count(*) FROM club AS t1 JOIN member_of_club AS t2 ON t1.clubid  =  t2.clubid JOIN student AS t3 ON t2.stuid  =  t3.stuid WHERE t1.clubname  =  "Bootup Baltimore" AND t3.age  <  18
Yaşından 18'in altında olan "Bootup Baltimore" kulübündeki üye sayısını sayın.