Example Question - given angle expressions

Finding the Value of x in Parallel Line Segments with Given Angle Expressions

\begin{align*} \text{Let } \angle ABC &= \angle BAC \text{ (alternate interior angles are equal because } AD \parallel BC) \\ 4x + 30^\circ &= 40^\circ \\ 4x &= 10^\circ \\ x &= \frac{10^\circ}{4} \\ x &= 2.5^\circ \\ \end{align*} \text{Round to the nearest tenth: } x = 2.5^\circ