Let us assume the time taken by the second jet to overtake the first jet = x
Let us assume the distance traveled by the second jet = d
Head start that the first plane gets over the second plane (d1) = 600 * (3/4)
                                                   = 150 * 3
                                                   = 450
Then
We get the equation for the second jet as
d = 800t
the equation of the first jet comes out to be
d - 450 = 600t
Now let us put the value of d from the first equation we get
d - 450 = 600t
800t - 450 = 600t
800t - 600t = 450
200t = 450
t = 450/200
 = 45/20
 = 2.25 hours
So from the above deduction we can conclude that it will take 2.25 hours for the second jet to overtake the first jet.
