Here A(0, 0, 6), B(0, 4, 0) and C(6, 0, 0) are the vertices of ΔABC.
Now D is mid-point of BC.
∴ Coordinates of D are
(

0+6

2

,

4+0

2

,

0+0

2

) = (3 , 2 , 0)
∴ AD = √(0−3)2+(0−2)2+(6−0)2
= √9+4+36 = 7 units
Also E is mid-point of AC
∴ Coordinates of E are (

0+6

2

,

0+0

2

,

6+0

2

) = (3 , 0 , 3)
∴ BE = √(0−3)2+(4−0)2+(0−3)2 = √9+16+9 = √34 units
Also F is mid point of AB
∴ Coordinates of F are
(

0+0

2

,

0+4

2

,

6+0

2

) = (0 , 2 , 3)
∴ CF = √(6−0)2+(0−2)2+(0−3)2 = √36+4+9 = 7 units