20. Rectangle $A B C D$ is divided into four parts by $C E$ and $D F$. It is known that the areas of three of these parts are $5$, $16$, and $20$ square centimeters, respectively. Therefore, the area of quadrilateral $A D O E$ is ( ) square centimeters.
考点：Geometric Model, Hourglass Model, Butterfly Model【Analysis】  
Connect FC  
(Hourglass), $S_{\triangle E O F}=5 \mathrm{~cm}^{2}, S_{\triangle C O D}=20 \mathrm{~cm}^{2}$  
Then $S_{\triangle C O F}=5 \times 2=10 \mathrm{~cm}^{2}, S_{\triangle B C F}=16-10=6 \mathrm{~cm}^{2}$.  
Using the half model D  
${ }^{\text {C }} S_{A D O E}=20+10-6-5=19 \mathrm{~cm}^{2}$