Answer:
I think the answer is 6 percent. 
their are 2 easy ways to understand... 
12 is multiplied with 1/2 ...
Their is no any other sign of - or +
so 12*1
 =12
 and, 
 12/2 =6
 or,
 12 is first multiplied with 2 then added with 1 again divided by 2 you will get the answer
 Let me know if I am right or wrong