Write a point-slope equation for the line with the given slope that contains given point.

m= -1; (-3, 6)

Given: m = -1, P1 = (-3,6), P2(x,y).

m=(y-6) / (x-(-3))
m=(y-6) / (x+3) = -1
Cross multiply:
(y-6) = -1(x+3).