Задача 10985.

Two starship with the engine off moving towards each other. One spaceship lit every second signal lights. On the opposite helicopter observed flashes every 1/2 second. Find the speed of spaceships rendezvous.

Detailed solution with a short recording conditions, laws and formulas used in the decision, the withdrawal of the calculation formula and the answer.
If you have any questions about the decision to write. I try to help.