speed=distance/time
s=d/t
t=d/s
1800/(2x+100)=750/x
1800x=750(2x+100)
1800x=1500x+75000
1800x-1500x=75000
300x=75000
x=75000/300
x=250
The rate(speed) of cargo plane is 250 miles per hour.
2x+100=2(250)+100=500+100=600
The rate(speed) of jet plane is 600 miles per hour.