Agnĳo has half as many apps as Sam who has a third as many apps as Naomi. Altogether, they have $$180$$ apps. How many apps does Sam have? 
Overseas Competition->Knowledge Point->Word Problem Modules->Questions Involving Sum, Difference and Multiples->Problems of Sum and Multiple
Let Agnijo have $$n$$ apps. Now Sam has $$2n$$, and Naomi $$6n$$. Therefore $$n+2n+6n = 9n = 180$$, and so $$n = 180\div9 = 20$$. Hence Sam has $$2\times20 = 40$$ apps. 