Answer:
x = 16 units
Explanation:
supplementary angles = 180°
so
3x + 5 + 9x - 17 = 180
12x - 12 = 180
12x = 180 + 12
12x = 192
x = 192 : 12
x = 16 units
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check
3 * 16 + 5 + 9 * 16 - 17 = 180
180 = 180
the answer is good