How Far Must a Gazelle Run to Escape a Cheetah?

[Cornraker]

Homework Statement

A cheetah can maintain its maximum speed of 100 km/hr for 30.0 seconds. What minimum distance must a gazelle running 80.0 km/hr be ahead of the cheetah to escape?

Homework Equations

What equation do i start his out with? I'm not even sure what to start lookinf or here.

The Attempt at a Solution

 

[rl.bhat]

Find the relative speed between cheetah and gazelle.
Then the minimum distance = relative speed X time.