SI. 2 In Figure $1, A B=A C$ and $A B / / E D$.
If $\angle A B C=P^{\circ}$ and $\angle A D E=Q^{\circ}$, find the value of $Q$.
$$
\begin{array}{ll}
\angle A B C=30^{\circ}=\angle A C B & \text { (base } \angle \mathrm{s} \text { isos. } \triangle \text { ) } \\
\angle B A C=120^{\circ} & (\angle \mathrm{s} \mathrm{sum} \text { of } \triangle \text { ) } \\
\angle A D E=120^{\circ} & (\text { alt. } \angle \mathrm{s}, A B / / E D) \\
Q=120 &
\end{array}
$$

Remark: Original question ... $A B / / D E \ldots$.
It is better for $A B$ and $E D$ to be oriented in the same direction.