1. Given that $\ell_1 \parallel \ell_2$ and $\ell_3 \parallel \ell_4$, and an angle of 108° is marked. 2. (a) To find $\angle 1$, note that $\angle 1$ and 108° are alternate interior angles formed by parallel lines and a transversal, so they are equal. $$\angle 1 = 108^\circ$$ 3. (b) To make $\ell_4$ perpendicular to $\ell_3$, $\angle 2$ must be 90° because perpendicular lines intersect at right angles. $$\angle 2 = 90^\circ$$