Answer: y = -4/5x - 12
1. First find slope. Since you are trying to find a line perpendicular to y = 5/4x + 10, the slope would be the negative reciprocal of 5/4x.
slope = - 4/5x
2. plug in (-5,-8) and the slope of -4/5 to the point slope form equation
(y-y2) = slope (x-x2)
= y+8=-4/5(x+5)
3. solve and simply y+8=-4/5(x+5)
y = -4/5x - 12 is your answer