Find the perimeter of the following shape, rounded to the nearest tenth: shape abcd is shown. point a is at -3,5. point b is at 2,6. point c is at 0, 2. point d is at -5, 1.

By turning the points into triangles and using Pythagorean theorem you can solve for the lonest side(of the triangle) which is Equal to that side.
AB     [(3-2)^2]+[(6-1)^2]=square root of (1+25)=Square root of 26= 5.099
If you do this for all 4 sides and add them up you get the  
P(perimeter)=19.1