[ Quadrilateral: calculations, metric relations.]

Diagonals $A C$ and $B D$ of the convex quadrilateral $A B C D$, whose area is 28, intersect at point $O$. Find the areas of triangles $A O B, B O C, C O D$, and $D O A$, given that the area of triangle $A O B$ is twice the area of triangle $C O D$, and the area of triangle $B O C$ is 18 times the area of triangle $D O A$.
Compose a system of equations.

## Answer

$6 ; 18 ; 3 ; 1$.