Given, AD is the median of triangle ABC.
So, AD will divide triangle ABC into two triangles of equal area.
Thus,
Area of triangle (ABD) = Area of triangle (ADC)
or, Area(△ABD)=12Area(△ABC) ... (1)
Again, E is the mid-point of AD. So, BE will be the median of triangle ABD.
So, Area of triangle (ABE) = Area of triangle (BED)
or, Area(△ABE)=12Area(△ABD)
Therefore, Area(△ABE)=14Area(△ABC) [using (1)]
Hence proved!!