Question 825733
(x-9)+(3x+15) = 90


x-9+3x+15 = 90


4x+6 = 90


4x = 90-6


4x = 84


x = 84/4


x = 21


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x-9 = 21 - 9 = 12


3x+15 = 3*21+15 = 78


So the smaller angle is <font color="red">12 degrees</font>