GMAT Problem Solving (PS) | A man cycling along the road noticed that every 12 minutes

Hi experts/Bunuel,

I did not understand as to how the overtake distance 'd' is equal to the meet distance 'd'. If it takes 12 and 4 minutes, does it not mean that the distance covered by overtake bus is different from the oncoming bus? Please clarify my not so profound doubt.

Warm Regards,
Karthik

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