Suppose $20 \textbackslash\%$ of $x$ equals $30 \textbackslash\%$ of $y$. What percentage of $y$ is $x$ ? (adapted from 2020 AMC 8, Question 15) 
选项为:A:$$5$$  B:$$35$$  C:$$75$$  D:$150$  E:$$300$$  请回答其中一个选项.