Question

Two planes start from the same airport and fly in opposite directions. the second plane starts 1/2 hour after the first plane, but its speek is 50 miles per hour faster. find the air speed of cach plan, if 2 hours after the first plante departs, the plans are 2000 miles apart

Answer 1

First plane
t = 2 hours.
r = r

Second plane
t = 1.5 hours
(30 minutes = 1/2 hour. the second plain has been in the air 2 - 1/2 hour = 1.5 hours. )
r = r + 30

Equation
2 * r + 1.5(r  + 50) = 2000
2r + 1.5r + 75 = 2000
3.5r = 2000 - 75
3.5r = 1925 
r = 1925 / 3.5
r = 550

the first plane was going 550 mph
the second plan was going 600 mph