The perpendicular slope is the negative reciprocal of the slope of the line it is perpendicular to. Therefore, the slope would be the negative reciprocal of -1/2 which would be 2.
From there, you plug in the coordinate into x and y and solve for b;
5 = 2 * -3 + b
5 = -6 + b
b = 11
Therefore the equation is;
y = 2x + 11
