Answer:
The length of the BC is 25 units .
Explanation:
As shown in the diagram
In ΔABC 
∠B = ∠C (As given)
(If the angles are equal than their opposite sides are also equal .)
Thus
AB = BC
As given
AB = 4x + 4
AC = 6x - 14
Thus
4x + 4 = 6x - 14
6x - 4x = 14 + 4
2x = 18

x = 9 
Put in the 
BC = 2x + 7
 = 2 × 9 + 7
 = 18 + 7
 = 25 units
Therefore the length of the BC is 25 units .