Answer:
4
Step-by-step explanation:
You can read the slope of the red line from the graph. It has a rise of 4 for a run of 1, so has slope 4/1 = 4.
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You also know that the slope of a perpendicular line will be the negative reciprocal of the slope of the given line:
-1/(-1/4) = 4
The slope of the red line is 4.
