Amount of money she spent to buy the cloth  $$\rightarrow$$＄$$4y-$$＄$$y$$  $$=$$＄$$3y$$,  Length of cloth she bought  $$\rightarrow$$＄$$3y\div $$＄$$7/\text{m}$$  $$= \frac{3y}{7}\text{m}$$. 
Mariam had ＄$$4y$$. After buying some cloth at ＄$$7$$ per metre, she had ＄$$y$$ left. How many metres of cloth did she buy? 
A) $$\frac{3y}{7}$$ 
B) $$\frac{5y}{7}$$ 
C) $21y$ 
D) $$35y$$ 