Answer:
m = -1
Explanation:
First write the line in slope intercept form y = mx+b where m is the slope and b is the y intercept
x-y = 6
subtract x from each side
-y = -x+6
Multiply each side by -1
y = x-6
The slope is 1
Perpendicular lines have slopes that multiply to -1
m * 1 = -1
m = -1
The slope of the perpendicular line is -1