
\[ MO = \frac{PA + QB}{2} \]
\[ PC = DQ = x \]
\[ Area(APQB) = \frac{PQ(PA+QB)}{2} = PQ\cdot MO \]
\[ Area(POQ) =\frac{PQ\cdot MO}{2} =\displaystyle\frac{1}{2} Area(APQB) \]
\[ Area(OPC)+Area(ODQ) = x\cdot MO \]
\[ Area(APC) + Area(BQD) = \frac{x\cdot PA} {2} + \frac{x\cdot QB}{2} = \frac{x(PA+QB)}{2} = x\cdot MO \]
Luego:
\[ Area(APC) + Area(COD) + Area(DBQ) = Area(POQ) = \displaystyle\frac{1}{2} Area(APQB) = Area(AOC) +Area(DOB) = \displaystyle\frac{1}{2}(Area(ACB)+Area(ADB)) = 10 \Longrightarrow{} \]
\( Area(APQB) = 20 \)