The graph shows two lines that cross at the point (5, 6) on the plane (see attached image).
This means that the point x=5 and y=6 belongs to both lines (is a solution for both equations representing the lines) and therefore this pair of values is the solution to both equations in the system.
Given that when X denotes the errors in an experimental transmission channel, when checked by a certifier that detects missing pulses. follows the cumulative density function as given below: