9514 1404 393
Answer:
(d) 9
Step-by-step explanation:
The relation you're supposed to apply here is ...
an exterior angle of a triangle is equal to the sum of the remote interior angles.
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The exterior angle is 17x+7, and it is equal to the sum of the two marked angles inside the triangle.
17x +7 = 13x +3 +40
4x = 36 . . . . . . . . . . . . . subtract 13x+7 from both sides
x = 9 . . . . . . . . . divide both sides by 4
