7 Given that the inverse function of $f(x)$ is $f^{-1}(x)$, if $f^{-1}(x)=\frac{x}{x+3}$, then the solution set of the inequality $f(x)>1$ is $\qquad$ .
(7) Since $f^{-1}(x)=\frac{x}{x+3}$, then $f(x)=\frac{3 x}{1-x}$, so the solution set for $f(x)>1$ is $\frac{1}{4}<x<1$.