7.2. The bisector of angle $ABC$ forms an angle with its sides that is three times smaller than the adjacent angle to $ABC$. Find the measure of angle $ABC$.
Answer. $\quad 72^{\circ}$. Solution. Let $x$ be the degree measure of angle $ABC$. From the condition of the problem, we get the equation $\frac{x}{2}=\frac{180-x}{3} \Leftrightarrow 5 x=360 \Leftrightarrow x=72$ (degrees).