The full answer is so long. I’m too lazy to do it but i can tell u how.
First write the equation of line AB then equation of line CD then compare the slope of both line AB and CD.

now, a line perpendicular to that one, will have a "negative reciprocal" slope, thus
5x-1= 26
5x-1+1= 26+1
5x= 27
Divide by 5 for 5x and 27
5x/5= 27/5
x= 27/5
Answer is x= 27/5 - A)
the answer to your question is n = -2