find the slope of any line perpendicular to the line through points (6,7) and (5,8).

a)-1
b)1
c)0
d)undefined

y2-y1/x2-x1 = slope

So...(8-7)/5-6) = 1/-1 = -1

The slope perpendicular to that would be the negative reciprocal of -1, which is 1.

Therefore, the slope is 1.