The supplementary angle to angle 2 is ∠5.
What are supplementary angles?
Supplementary angles are angles that do complement or supplement each other and the addition of these angles result to the sum of angle on a straight line. (i.e. the addition of these angles = 180 degrees).
In the given question, ∠2 is a right angle triangle and a right angle triangle is 90 degrees.
In the attached diagram, the angle must supplement ∠2 must also be a right angle triangle i.e. 90 degrees.
As such, we can conclude from the diagram that the angle that supplement angle 2 is ∠5.