$$(11+ 11 + 11 + 11 + 11 + 11)-(9 + 9 + 9 +9 +9 +9)=$$． 
Overseas Competition->Knowledge Point->Calculation Modules->Whole Numbers->Whole Numbers Addition and Subtraction 
Rearranging: $$11-9 +\cdots + 11-9 =2+\cdots +2 =2\times6 = 12$$. 