Answer:
x = 5
Explanation:
the supplementary angle of (19x-18) = 180 - (19x-18) = 198-19x
all interior angles of a triangle = 180 degrees
180 = (7x+1) + (10x-9) + (198-19x)
180 = 7x+10X-19x+1-9+198
180 = -2x+190
-2x = -10
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