Answer:
BC = 28
Explanation:
Since the triangle is equilateral then all 3 sides are congruent.
Equate AB and AC and solve for x, that is
12x + 4 = 8x + 12 ( subtract 8x from both sides )
4x + 4 = 12 ( subtract 4 from both sides )
4x = 8 ( divide both sides by 4 )
x = 2, thus
AC = 8x + 12 = (8 × 2) + 12 = 16 + 12 = 28
Since the 3 sides are congruent then BC = 28