Supplementary angles is when 2 angles add up to 180 degrees.
We will name the smaller angle a and the bigger angle b.
therefore:
b - 172.6 = a
a + b = 180
Now we substitute:
a + b = 180
b - 172.6 + b = 180
2b - 172.6 = 180
2b = 352.6
b = 176.3
To find a:
a + b = 180
a + 176.3 = 180
a = 3.7
Therefore,
angle a = 3.7 degrees
angle b = 176.3 degrees.
Hope it helps and have a great day ahead