Hint $1.$ How to approach the problem

At any time, the displacement of point O is given by the algebraic sum of the displacements of the two pulses at that point.

Hint $2.$ Displacement of point O if only one pulse were present

Let be a short interval of time after the two pulses have begun to overlap. If only the pulse coming from the right were present, the

displacement of point O at time would be $.$ What would its displacement be if only the other pulse were present?

Express your answer in terms of $.$

Hint $1.$ Inverted pulses

Keep in mind that the two pulses are identical but inverted; thus their displacements are equal magnitude but opposite