Answer:
To the right relative to the original frame.
Explanation:
In first reference frame <em>S</em>,
Spatial interval of the event,
Temporal interval of the event,
In the second reference frame <em>S'</em>, the two flashes are simultaneous, which means that the temporal interval of the event in this frame is
The speed of the frame <em>S' </em>with respect to frame <em>S</em> = v.
According to the Lorentz transformation,
And positive v means the velocity of the second frame<em> </em><em>S'</em> is along the positive x-axis direction, i.e., to the right direction relative to the original frame <em>S</em>.