13.050. The worker's wages for October and November were in the ratio of $3 / 2: 4 / 3$, and for November and December, they were in the ratio of $2: 8 / 3$. In December, he received 450 rubles more than in October, and for exceeding the quarterly plan, the worker was awarded a bonus of $20 \%$ of his three-month earnings. Find the size of the bonus.
Solution.

Let $x$ rubles be the worker's salary for November. Then for October, it is $\left(\frac{3}{2} : \frac{4}{3}\right) x = \frac{9}{8} x$ rubles; for December, it is $\left(\frac{8}{3} : 2\right) x = \frac{4}{3} x$ rubles. According to the condition, $\frac{4}{3} x = \frac{9}{8} x + 450$, from which $x = 2160$ rubles - the salary for November; $\frac{9}{8} \cdot 2160 = 2430$ rubles - for October; $\frac{4}{3} \cdot 2160 = 2880$ rubles - for December. Then the bonus amount is $-(2160 + 2430 + 2880) \cdot 0.2 = 1494$ rubles.

Answer: 1494 rubles.