Answer: 55°
Step-by-step explanation: To solve this problem, we will first need to look at the definition for supplementary angles. On my whiteboard, I have written the definition of supplementary angles. First take a look at that and give yourself time to understand. I have also shown a different example.
Since supplementary angles add up to 180° and we already know one of our angles, we can find its supplement by subtracting 125 from 180.
180 - 125 gives us 55.
This means that the supplement of 125° is 55°.