$$\frac{10}{25}\textasciitilde\textbackslash$ \text{/lb}=0.4\textasciitilde\textbackslash$ \text{/lb}$$  $$\frac{15}{35}\textasciitilde\textbackslash$ \text{/lb}=0.43\textasciitilde\textbackslash$ \text{/lb}$$  $$\frac{10}{25}\textless\frac{15}{35}$$  So, the answer is $$A$$. 
Lisa is buying potatoes at a grocery store. She can either spend $10$ dollars on a $25\text{-lb}$ bag or $15$ dollars on a $35\text{-lb}$ bag. Whic is the cheaper one? 

1. The $25\text{-lb}$ bag 
2. The $35\text{-lb}$ bag 