Su Li has the same number of ten-cent and fifty-cent coins. The total value is ＄$$6$$. How many coins does she have in all? 
Overseas Competition->Knowledge Point->Word Problem Modules->Unitary Method Problems->Finding the Total Value using Unitary Method
$$10u + 50u = 600$$  Thus, $$1u = 10$$, in total we have $$2u=20$$ 