1. According to the properties of a parallelogram, the total value of the angles that adjoin one of its sides is 180 °. Considering this, the angle BAD = 180 ° – 150 ° = 30 °.
2. Draw the BH height to the AD side.
3. In the formed triangle ABH, the height BH is a leg opposite an angle of 30 °. Therefore, its length is equal to 1/2 the length of the hypotenuse AB:
BH = AB: 2 = 20: 2 = 10 cm.
4. The area of the parallelogram = AD x AH = 12 x 10 = 120 cm ^ 2.
Answer: the area of the parallelogram ABCD = 120 cm ^ 2.
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