Respuesta :

1/2n + 9 = 27 
         - 9   -  9 
----------------------
1/2n = 18 
------   --------
1/2      1/2n

n = 36
its 36 that is just a system called Begin Oppositive Divide or B.O.D you begin from the 27 then you do the oppositive of -/+ 9 then you divided by 1/2 and is equals to 36. 

HOPE THIS HELPS!!!!
ACCESS MORE