The display is 1024 x 768, so the number of pixels is 1024*768 = 786,432.
It takes 1 second to draw these number of pixels 75 times.
The drawing rate is
(75*786,432 pixels) per second
The length of the pulse to draw a pixel is
1/(75*786432) s = 1.6954 x 10⁻⁸ s = 0.1695 x 10⁻⁹ s= 0.1695 ns
Answer: 0.17 ns (nanosecond) or 1.695 x 10⁻⁸ s