13.001. Of the four given numbers, the first three are in the ratio $1 / 5: 1 / 3: 1 / 20$, and the fourth number is $15 \%$ of the second number. Find these numbers, given that the second number is 8 more than the sum of the others.
Solution.

The required numbers are: $k / 5 ; k / 3 ; k / 20 ; 0.15 \cdot k / 3=k / 20$. According to the condition $\frac{k}{3}-8=\frac{k}{5}+\frac{k}{20}+\frac{k}{20}$, from which $k=240$.

Answer: $48 ; 80 ; 12 ; 12$.