Answer:
x=54∘
Step-by-step explanation:
∙ the diagonals bisect the angles
∙ the diagonals bisect each other at right angles
∙ opposite sides are parallel
BD is a diagonal and bisects ∠ADC
⇒∠ADB=∠CDB=x
⇒∠ADB=∠CDB=x → alternate angles
the sum of the angles in the lower triangle = 180 ∘
⇒ 36∘ + 90∘ + x = 180∘
⇒ x=180 - 36 - 90 = 54∘
