Let O be centre of the semicircle.
M be the mid-point of BC.
X be the point on DC such that AX is perpendicular to DC.
Area of trapezium = area of rectangle with AX as height and OM as width = AX x OM
Triangle ADX is similar to triangle OME.
Therefore, AD/AX = OM/OE
so AX x OM = AD x OE = 14 x 7 = 98.