Physics Question from JEE Main 2023 · 30 January, Shift 1

A horse rider covers half the distance with $5 \, \text{m/s}$ speed. The remaining part of the distance was travelled with speed $10 \, \text{m/s}$ for half the time and with speed $15 \, \text{m/s}$ for other half of the time. The mean speed of the rider averaged over the whole time of motion is $\frac{x}{7}$ $\text{m/s}$. The value of $x$ is: