Answer
$75^{\circ}, 45^{\circ}, 120^{\circ}$
Work Step by Step
1. Given 2 interior angles and 1 exterior angle of the triangle. We can use extrerior angle to find the third interior angle of the triangle. We just need to subtract the exterior angle from 180 degrees.
$180^{\circ}-(9x-12)^{\circ}=-9x+168$
2. The sum of interior angles of the triangle equal to the 180 degrees
$(6x+3)^{\circ}+(4x-3)^{\circ}+(-9x+168) ^{\circ}=180^{\circ}$
3. Solve the equation for x:
$x+168=180$
$x=12^{\circ}$
4. Then find all the angles by replacing x=12:
$6(12)+3=75^{\circ}$
$4(12)-3=45^{\circ}$
$9(12)+12=120^{\circ}$
