jmc

Let the popularity of a television (or the number of customers who buy one) equal $p$, and let the cost of the television equal $c$. According to Daniel's theory, $p$ and $c$ are inversely proportional. Thus, $(p)(c)=k$ for some constant value $k$. If $p=15$ when $c=1500$, then $k=(15)(1500)=22500$. So when $c=2500$, $$\begin{array}{rl}(p)(c)& =k\\ \Rightarrow (p)(2500)& =22500\\ \Rightarrow p& =\frac{22500}{2500}\\ & =\boxed{9}.\end{array}$$According to Daniel's theory, 9 customers would buy the \2500$ television.