5. From the start to the finish, flags are placed at equal distances from each other. An athlete runs the distance from the first flag to the eighth in 8 seconds. How long will it take him to reach the twelfth flag?
5. Since the athlete runs seven (not eight, as is sometimes thought) intervals between the flags in 8 seconds, he will run 11 intervals in $\frac{8 \cdot 11}{7}=12 \frac{4}{7}$ seconds.