16. In the figure below, the numbers labeled at 8 vertices: $a, b, c, d, e, f, g, h$, each of these numbers is equal to $1/3$ of the sum of the numbers at the three adjacent vertices. Find: $(a+b+c+d)-(e+f+g+h)$.

 untranslated part:
 
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Note: The last sentence is a note and not part of the problem statement, so it is not translated.
16.【Solution】From the given conditions, we know
$$
\begin{array}{l}
a=\frac{b+e+d}{3}, b+e+d=3 a \\
b=\frac{c+f+a}{3}, c+f+a=3 b \\
c=\frac{d+g+b}{3}, d+g+b=3 c \text { (3) } \\
d=\frac{a+h+e}{3}, a+h+e=3 d \text { (4) } \\
\text { (1) }+ \text { (2) }+ \text { (3) }+(4), \text { then } 2(a+b+c+d)+(e+f+g+h)=3 \\
(a+b+c+d)
\end{array}
$$

which means $e+f+g+h=a+b+c+d$
$\therefore$ The required value is 0.