Al ran twice as far as Bob ran. They ran a total off $$18\rm km$$. How far did Al run? 
Overseas Competition->Knowledge Point->Word Problem Modules->Questions Involving Sum, Difference and Multiples->Problems of Sum and Multiple
Al ran twice as far as Bob. Split $$18\rm km$$ into two parts, one twice the other, to see that Bob ran $$6\rm km$$ and Al ran twice as far, $$12\rm km$$. 