What a^2-2a-3=0 by solving equations by completing the square

Apark is in the shape of a rectangle. the park authorities are planning to build a 2-meter-wide jogging path in the park (shown as the shaded region in the image). what is the area of the jogging path? plz

Can someone me and plz do the problem

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)