Answer:
∠3
Step-by-step explanation:
Supplementary angles are angles that add up to 180°. Angle 6 is a right angle, so it's worth 90°. This means that the other angle(s) have to be 90° as well.
As you can see, the other angle with 90° is angle 3, thus, making it the correct answer.
Have a lovely rest of your day/night, and good luck with your assignments! ♡
