|x/2| + |y/2| = 5

|x| + |y| = 10

with this we can come up with the following equations:

(x+y)=10; (x-y)=10
(-x-y)=10; (-x+y)=10

The slopes of the equations are -1, 1, -1, 1

solving the above equations you will get the following points:
(0,10); (10,0); (0,-10); (-10,0).

plot this on the graph and you will get a square with sides sqrt200.

Hence area of the square will be a^2 = 200

check the graph below

Thanks mals24!
I still am not sure of how you came up with the 4 co-ordinates though.
I understood the 4 equations. [Thanks, cuz that atleast got me started]
Then, did you arrange each equation in the form y = mx + c and then find the X and Y intercept for each equation? Or is there any other way to deduce the coordinates from the corresponding slopes of 1 and -1.

yup you can change the equations in y=mx+c form n then find the co-ords for each equation.