其它
Suppose $15 \textbackslash\%$ of $x$ equals $20 \textbackslash\%$ of $y$. What percentage of $x$ is $y$ ? (2020 AMC 8, Question 15) 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Percentages Word Problems
Since $20 \textbackslash\%=\frac{1}{5}$, multiplying the given condition by 5 shows that $y$ is $15 \cdot 5=(\mathbf{C}) 75$ percent of $x$. 