Use \(\text{speed}=\dfrac{\text{distance}}{\text{time}}\).

So \(\text{speed}=\dfrac{120}{15}=8\text{ m s}^{-1}\).

Use \(\text{distance}=\text{speed}\times \text{time}\).

So distance \(=9\times 7=63\text{ m}\).

Use \(\text{time}=\dfrac{\text{distance}}{\text{speed}}\).

So \(t=\dfrac{150}{25}=6\text{ s}\).

To use \(t=\dfrac{s}{v}\) directly, we model the motion with a constant speed over a fixed distance.

A suitable assumption is that the prey does not move and the hunter runs straight at constant speed from the start.

First convert the distance to metres:

150 million km \(=150\times 10^6\times 1000=1.50\times 10^{11}\) m.

Then

\(t=\dfrac{1.50\times 10^{11}}{3.00\times 10^8}=500\text{ s}\).

500 s \(=8\) min 20 s.