Angle ADC is a linear pair ( 180° )



=> BDE = 68°
Similarly,
BCE is a linear pair or straight line.
BEC = BED + DEC
=> 180° = BED + 126°
=> BED = 180° - 126°
=> BED = 54°
As we know that Sum of angles of triangle is 180° .
m + 68° + 54° = 180°
=> m + 122 = 180°
=> m = 180° - 122°
=> m = 58°
The value of m is 58° .