Answer:

Explanation:
Perpendicular lines means that their slopes are negative reciprocals of each other.
In other words, when you multiply the 2 slopes, that will gives us -1.
Slope's formula is m =

- Taking the first two points, we have:

- Taking the second two points, we have:

Now multiplying these 2 expressions and equating it to -1, we can solve for x:

x = -9