Answer
60°
Explanation
In the beginning, the measure of angle 1 is 55°.
After line y is rotated 5° clockwise about the point of intersection, the measure of angle 1 is 60° (= 55° + 5°).
Given that angles 1 and 3 are vertical angles, then they are congruent, that is,
![\begin{gathered} m\angle3=m\angle1 \\ m\operatorname{\angle}3=60\text{ \degree} \end{gathered}]()