In $$20$$ years, Li will be $$3$$ times as old as he is now. How old will he be in $$10$$ years? 
Overseas Competition->Knowledge Point->Word Problem Modules->Age Problems->When..., When... Type Age Problems
In $$20$$ years, Li will be $$3$$ times his age now, so $$20$$ must be twice his age now. Thus, Li is $$10$$ now and will be $$20$$ in $$10$$ years. 