Geometry math question no Guessing and Please show work

Answer is A. -5/4
Perpendicular lines are the negative reciprocal of each other. A reciprocal is when the denominator and numerator is switched.
For example, y= 2x would be perpendicular to Y= - 1/2x
So in the situation the 5 and 4 are switched and then a negative sign would be added.
A.
You flip the fraction and the subtraction fromt the fraction and whole number makes it a negative. So negative 5/4