7. Given positive rational numbers $a, b$, (both not 0, and $a+b+c=abc$ then $\frac{a}{b}+\frac{a}{c}+\frac{b}{a}+$ $\frac{b}{c}+\frac{c}{a}+\frac{c}{b}-ab-bc-ca=$ $\qquad$ .
7. -3
$\frac{a}{b}+\frac{c}{b}-a c=\frac{a+c-a b c}{b}=-1$ and the rest are similar.