So all around is 360 degrees. The sides directly in front of each other are congruent.
(5z+8) + (4z+20) + (5z+8) + (4z+20) = 360 There is two of each one because of the congruent sides. Combine like terms. 18z + 56 = 360 Get the variable by itself. 18z + 56 = 360 -56 -56 18z=360 divide by 18
z = 20
Hope this helps! If you have any questions, just ask!
