To find the slope of a line that is perpendicular to the given line, we find the negative reciprocal of the given slope (flipped and made negative), so ½ would become -2/1 or simply -2. This gives us the equation y=-2x+b. To find b we plug in the coordinates the new line has to pass through, so ((-5)=-2(10)+b) = (-5=-20+b) = (15=b) or (b=15). So, the answer would be A. y=-2x+15