A boat took 4 hours to make a downstream trip with a current of 6km/h the return trip against the same current took 6 hours find the speed of the boat in still water

Aline is perpendicular to another line m2= (-1/m1), where m1 is the slope of the original line and m2 is the slope of the perpendicular line. which of the following equations represents the line that passes through the point (-2,1) and is perpendicular to the line below?