Because ABCD is a parallelogram, angle(D) = 60°.
Because AB || DC. the alternate interior angle below the letter A is also 60°.
Angle(A) = 90° - x°.
Thus the three angles to the left of diagonal line through A are: (90° - x°) + 60° + 2x° = 180°.
Solving: 150° + x° = 180° ---> x = 30°