## Thinking Mathematically (6th Edition)

$x=9^\circ$ The two angles are: $12\times 9^\circ-3^\circ=105^\circ$ $10\times9^\circ+15^\circ=105^\circ$
The two given angles are alternate interior angles, which means that they are equal. $12x-3^\circ=10x+15^\circ$ $2x=18^\circ$ $x=9^\circ$ The two angles are: $12\times 9^\circ-3^\circ=105^\circ$ $10\times9^\circ+15^\circ=105^\circ$