To solve this problem I aways start with the question . In this case the size of each angle is required .
So we can call this unknown smaller angle be x. Let the supplementary angle be y
Since the supplementary angles together equal 180 degrees the following equations are determined to keep things very simple:
x + y = 180
y = x+178
solving for y :
180- y =x
or y =180-y+178
2y= 358
y=179
x=1