Answer:
x = 15
Explanation:
The two angles form a straight line so they add to 180 degrees
3+6x + 5x+12 = 180
Combine like terms
11x+15 = 180
Subtract 15 from each side
11x+15-15 =180-15
11x = 165
Divide by 11
11x/11 =165/11
x =15
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