Using the general format of a line, y = mx + c,
Where m = slope of the line, c = vertical intercept.
y = -3x -3, comparing to y = mx + c
Slope, m = -3, vertical intercept, c = -3.
For a negative slope, the line would be falling downwards from the left hand side of graph sheet to right hand side.
Slope = -3,
Vertical or y intercept is the point it cuts across the y axis, at this point, x = 0
y intercept = (0, -3)
x intercept, at this point, the value of y is zero.
y = -3x - 3
0 = -3x - 3
0 + 3x = -3
3x = -3
x = -3/3
x = -1.
x intercept = (-1, 0)
So we would plot the points (0, -3) and (-1, 0)
See attached picture for sketch of the line y = -3x - 3.