Answer
See the detailed answer below.
Work Step by Step
As we see in the figure below, observer 1 sees that train 2 is shorter than his train since train 2 is moving at speed of $v$ to the left while train 1 is stationary.
So, when the first strike occurs when the two ends of the trains are aligned, the two observers notice it.
After a while observer on train 1 notice the second strike but he still saw that train 2 does not reach the other end of his train yet so he still thought that observer 2 does not see the second strike.
But according to observer 2, the two trains are the same length, so the two strikes occur simultaneously.
