A picture can help you sort this out.
Draw point E on CD so that AE ⊥ CD. Then the distance DE is 8cos(60°) = 4, and the height AE is 8sin(60°) = 4√3. The length of CD is 8+2×4 = 16. The area of the trapezoid is the product of the height and the average base length:
... A = (b1 +b2)/2×h = (8 cm + 16 cm)/2×(4√3 cm) = 48√3 cm² ≈ 83.14 cm²
