Answer:
The first choice (12)
Step-by-step explanation:
i'm not 100% what the theory is but here is how I did it:
the angle D and 115% are supplementary which means they add up to 180.
115+x=180
x=65
so now that you know all the angle measures, you also know that all angles of a triangle add up to 180.
65+3x+19+5x=180
combine like terms:
8x+84=180
subtract 84 from both sides:
8x=96
divide by 8 on both sides
x=12
