Explanation:
I like to think of supplementary angles as "supper" that's bigger than a "complimentary" snack. So supplementary angles are 180° in total, while complimentary angles are 90°.
To find the supplementary angle for 3, you look for straight lines, which are also equal to 180°. So for 3, both 1 and 4 would be supplementary. If you added 4 to 3, it would add up to 180°, and if you added 1 to 3 it would make a straight line (180°)
5 is the same, but backwards. 6 and 7 would be the supplementary angles because they are next to each other, part of a straight line.