*Urgent 7th Grade Math Help*!?

Okay, what you need to do is to get a sheet of paper, and draw a picture. I know, I know, but it actually helps for those of us who aren't super geniuses. So if the first plane is going at 600km/h, then when the second plane takes off, it will be (600)x(3/4) km away, which is 450. Given that the planes both keep moving, in another 1/4 of an hour, the first plane will have gone the remaining 150, and the second plane will have gone a total of 200 km. Now our plane 1 is at 600 km, and our plane 2 is at 200 km, and our time is exactly 1 hour into travel. In another 1/4 of an hour, the first plane will go another 150 km (750 total) and the second will go another 200 (400 total). Another 1/4 of an hour the first plane will go 150 (900 total) and the second another 200 (600 total). You keep going like this, adding 150 to the first, and 200 to the second, and keeping track of time (so far it is 1hr and 1/2). At 3 hours, they are at the same point (1800 miles). Good luck with your homework.