2 rockets are launched the first one travels 9000mph 15 minu

2 rockets are launched. the first one travels 9000mph. 15 minutes later the second is launched at 10000mph. What is the distance at which both rockets are an equal distance from earth.
Please help me set up the equation.
Thank you

Solution

Let the unknown distance be \"x\".
Nine Thousand mph rocket data:
distance = x; rate=9000mph; time= (x/9000)hrs.
Ten Thousand mph rocket data:
distance = x; rate=10000mph; time= (x/10000)hrs.
EQUATION:
time-time= (1/4)hr.
x/10000 -x/9000 = 1/4
[9000x-10000x)/(9E7)=1/4
1000x=9E7/4
x= 9E7/4000
x= 22500 miles