Y=2/3x-5 and 4x-8y=11

P = 18.4 units

Step-by-step explanation:

Sides AB and CD are congruent and thus have the same length.

Sides AD and BC are congruent.

The length of side AB is found using the Pythagorean Theorem:

|AB| = √ [ 5² + 1² ] = √26

and

|BC| = √ [ 4² + 1² ] = √17

Then the perimeter is P = 2(√26) + 2(√17), or

                                           10.20    +  8.25, or, to the nearest tenth,

                                      P = 18.4 units