I am not able to understand the question from the following link.Please explain it in a easy way.
CBSE Class 11th Physics NCERT Solution Page 59 Question 3.26

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What a poorly worded homework question. It seems the 'x' variable is the stones' altitude, and that while not explicitly stated the initial velocity provided is measured in the positive vertical direction. Write the equations of motion x(t) for the two stones, and find their difference x2-x1.