80. Find a set of numbers, where the first, added to a third of the third, equals the second, and the second, added to a third of the first, equals the third. The third is also greater than the first by 10.
80. System of equations:

$$
\begin{array}{r}
x+\frac{1}{3} z=y \\
y+\frac{1}{3} x=z \\
z-x=10
\end{array}
$$

From (1) and (2): $2 x=z$, therefore, from (3) $x=10 ; z=20$; $y=16 \frac{2}{3}$.