Let's write lines in the form y = mx+c. If your line passes through the point with x=-2, y=3 then 3 = -2m + c. Now if lines y = mx + c and y = nx + d are perpdendicular then the slopes m and n are related by mn = -1. So your line has slope m = -1/2, being perpendicular to a line with slope 2. That gives you c=2.