I'm currently in the process of trying to learn how to use quadratics to find out speed/distance/time etc. My program that I'm taking is often very unclear and skims over topics regularly. The example I was given to learn the process was fairly straightforward and easy to learn, however the question I have to answer for my work is different. The first example I was given is:

A jet flies 4200km from point A to point B. On the return trip the speed was increased by 100km/h. The total trip time is 13 hours. What is the jets speed from point A to point B?

So they include distance = speed * time or time = distance / speed and that the equation should look something like this : 13 = 4200/x + 4200/(x+100)

After simplifying it should look like (13x^2)-7100x-420000=0 and factoring it to find the roots makes it look like (13x+700)(x-600)=0 The roots are: x=-53.846 and x=600

With this we know the speed is 600 because a negative number makes no sense.

Ok moving on. So the question I need help with is very similar except a very key component.

A jet flies 4800km from tokyo to bangkok. On the return trip the speed is decreased by 200km/h. If the difference in the times of flights was 2 hours, what was the jets speed from bangkok to tokyo?

So after spending quite a while just trying to piece together different combinations of numbers I've concluded that I have no idea where to start, and these people just love messing with us. I have no clue what I'm doing without the total trip time because that's just how they taught us.

If anybody would be able to help me I'd greatly appreciate it,

Thanks very much