To determine the measure of angle DBC, we can refer to a common geometry problem scenario involving an equilateral triangle and an sceles triangle inside it:

Key Observations (Assuming the standard figure):

• Let $\triangle ABC$ be an equilateral triangle, so all angles are $60^\circ$ and all sides are equal.
• Point $D$ is inside $\triangle ABC$ such that $DB = DC$ (sceles $\triangle BDC$) and $\angle BDC = 120^\circ$.

Calculation:

In $\triangle BDC$:

• $DB = DC$, so it’s sceles with $\angle DBC = \angle DCB$.
• The sum of angles in a triangle is $180^\circ$.

Thus:
$\angle DBC + \angle DCB + \angle BDC = 180^\circ$
$2\angle DBC + 120^\circ = 180^\circ$
$2\angle DBC = 60^\circ$
$\angle DBC = 30^\circ$

Answer: $\boxed{30}$

作者声明:本文包含人工智能生成内容。