#12:
Assuming that I have those points correct: (1, 5) and (-4, -10), the slope of this line is
5-(-10)
m = --------------- = 15/5 = 3
1-(-4)
The line passes thru the origin, so the y-intercept is 0.
So the equation of this line is y = 3x.
I see no marks (points) in the illustration for #13.
