Answer:
12
Explanation:
Assume that those angles' curve in the triangle have same measure.
Law of Sin states that:

From the question, assume that B and C are congruent or have same measure. Let B and C be congruent; angle B = angle C thus:-

Let b = x and c = 12; for angle B, it's not given so leave it.

Multiply both sides by LCM which is 12x.

Divide both sides by sinB.

Therefore, x = 12.