Hello, Rimas!
An interesting problem . . . Did you make a sketch?
If two equilateral triangles of area A intersect to form a regular hexagon,
then what is the area of the hexagon? Code:
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Each equilateral triangle is comprised of nine smaller triangles.
They overlap in a hexagon comprised of six triangles.
The hexagon has an area which is $\displaystyle \frac{6}{9} = \frac{2}{3}$ of an equilateral triangle.
Area of hexagon: .$\displaystyle \frac{2}{3}A$