(7) Let $a, b, c$ be non-negative real numbers, then the minimum value of $\frac{c}{a}+\frac{a}{b+c}+\frac{b}{c}$ is
7: According to the AM-GM inequality, we get
$$
\begin{aligned}
\frac{c}{a}+\frac{a}{b+c}+\frac{b}{c} & =\frac{c}{a}+\frac{a}{b+c}+\frac{b+c}{c}-1 \\
& \geqslant 3 \sqrt[3]{\frac{c}{a} \cdot \frac{a}{b+c} \cdot \frac{b+c}{c}}-1 \\
& =2 .
\end{aligned}
$$