Hi,
Recall that the area of a parallelogram is the product of the base b and the height or "altitude" h. So the formula is : b * h. b = 20 here, and h = 6, so we get : 20 * 6 = 120.
Now we have to compute the area of the semicircle, remember the formula for the area of a circle is : πr² where r is the radius of the circle. If we watch the figure, we already have the value of the diameter d = 8. So the radius is equal to half the diameter : r = 8 /2 = 4
Now applying the formula we get : πr² = π * 4² ≈ 50.3 rounded to the nearest tenth place.
But we don't wont the area of the circle, we want half the area of it, since it's a semicircle : πr² / 2 ≈ 25.1 rounded to the nearest tenth place.
Now to get the whole area of the figure, we need to sum the area of the parallelogram with the area of the semicircle : 120 + 25.1 ≈ 145.1 rounded to the nearest tenth place.
Good Luck