Answer:
x = 51°
Explanation:
In a rhombus, the diagonals bisect the angles, thus
∠ BAE = ∠ DAE = 39° , then ∠ A = 78°
∠ ADE = ∠ CDE = x , then ∠ D = 2x
In a rhombus, consecutive angles are supplementary
∠ A and ∠ D are consecutive angles , thus
78 + 2x = 180 ( subtract 78 from both sides )
2x = 102 ( divide both sides by 2 )
x = 51°