Since you are unable even to begin, I'll assume that you missed the class(es) when this was covered, and need lesson instruction.
This topic is often referred to as a "uniform rate" or "uniform motion" exercise, using the equation "d = rt". You can find loads of lessons online, such as this one, which explain how to set up and solve these sorts of exercises. Please study at least two from this list. Once you have learned the basic terms and techniques, please attempt the exercise.
If you get stuck, please reply showing your thoughts and efforts so far, starting with the variables you picked, and how you defined them. Thank you!
thanks so much but I actually figured it out already. I just had a bit of a panic attack when I posted this, but I still really appreciate the quick response. I now see the answer would be 300 km/hr...sorry for wasting your time.