Thank you for the opportunity to help you with your question!

Well. this question is about relative speed.

When calculating speed for objects moving towards each other, we add their individual speeds.However, when calculating speed for objects moving against one another we subtract them

The relative speed is 75+75=150 kph

Distance =6 km

time taken for them to reach each other=Distance between them/relative speed

=6/150=0.04 hours

We are supposed to change the time into minutes

1 hour= 60 minutes

0.04 minutes=?

T=0.04x60

2.4 minutes

Please let me know if you need any clarification. I'm always happy to answer your questions.