You know that the two angles make up a perfectly flat line, which is a 180° angle. So we can create the equation:'
3x + 10 = 12x
Now solve for 'x'. Subtract 3x to both sides:
10 = 9x
Divide 9 to both sides:
x = 10/9
We want to find the smaller angle, so put this value in for 'x' in '3x + 10':
3x + 10
3(10/9) + 10
30/9 + 10
13 1/3°
