13.014. Find three numbers if the first is $80 \%$ of the second, the second is related to the third as $0.5: 9 / 20$, and the sum of the first and third is 70 more than the second number.
Solution.

Let $x$ be the first number, $y$ be the second number, and $z$ be the third number.

Then, according to the condition, $\left\{\begin{array}{l}x=0.8 y, \\ \frac{y}{z}=\frac{0.5}{9 / 20}, \\ x+z=y+70 .\end{array}\right.$ Solving the system, we get $x=80 ; y=100 ; z=90$.

Answer: $80,100,90$.