When a pair of parallel lines is intersected by a transversal, then
Corresponding angles are equal.
∠2 and ∠6 are corresponding angles.
So, m∠2 = m∠6
=> m∠2 = 123.5°
We know that linear pair of angles are supplementary (180°).
∠1 and ∠2 are linear pair of angles.
So, m∠1 + m∠2 = 180°
=> m∠1 + 123.5° = 180°
=> m∠1 = 180° - 123.5°
=> m∠1 = 56.5°