The cost of my algebra book is $$200\textbackslash\%$$ of that of my geometry book.  The cost of my geometry book is $$\frac{4}{3}$$ that of my calculus book. If my calculus book costs ＄$$21$$, how much do all $$3$$ books cost together? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Knowing the Base
The cost of the calculus book is ＄$$21$$. The cost of my geometry book is ＄$$21\times \left(\frac{4}{3}\right)=$$＄$$28$$. My algebra book costs ＄$$28 \times2 =$$＄$$56$$. All $$3$$ books cost ＄$$21+$$＄$$28 +$$＄$$56 =$$＄$$105$$ in total. 