Answer:
x = 10
Explanation:
y = - 8 is a horizontal line parallel to the x- axis
A line perpendicular to it will therefore be a vertical line parallel to the y- axis with equation
x = c ( c is the value of the x- coordinates the line passes through )
the line passes through (10, - 20 ) with x- coordinate 10 , then
x = 10 ← equation of perpendicular line