Question 1 is unclear to me, so I assume you want to say that the planes leave from same airport and you want to find the time when they are 450 kms apart.

Solution 1)

Let t be the time required for these two plane be 450 kms apart.

So distance (x) travelled by plane A in t hours = 960t (since distance = speed * time)

and distance (y) travelled by plane B in t hours = 810t

Given, plane A is 450 kms ahead of plane B in t hours.

So, x = y + 450

=> 960t =810t +450

=> 960t - 810t = 450

=> 150t = 450

=> t =450/150 = **3 hours**

So it will take 3 hours for plane A to get 450 kms ahead.

Solution 2)

Distance travelled by bus A be x in t time.

Distance travelled by bus B be y in t time.

x = 80t

y = 108t

Given, they are moving in opposite direction so sum of the distance should be equal to 329km at time t.

x + y =329

=> 80t + 108t = 329

=> 188t = 329

=> **t =1.75 hours **

**or t = 1 hour 45 minutes**

**or t = 105 minutes**