Answer: -4
There's no diagram or photo of this question. I'm just assuming the red line is perpendicular to the green line.
The perpendicular line is always the reciprocal to the other. -1/4 is the slope of the green line. The red line would be -4, since it's the reciprocal of -1/4.
I'm sorry if I did the wrong line, but there's no diagram.
