13.352. A girl, an acquaintance of a young man sitting by the window of a tram, was walking towards the moving tram. 8 seconds after she passed by the window, the young man got off the tram and followed her. How much time passed from that moment until he caught up with the girl? The young man's speed is twice the girl's speed and five times less than the tram's speed.
Solution.

Let $x, 2x, 10x$ be the speeds of the girl, the boy, and the tram, respectively. According to the problem, $8 \cdot x + 8 \cdot 10x + t \cdot x = t \cdot 2x$, where $t$ is the desired time. Solving the equation, we find $t=88$ (s).

Answer: 88 s.