Answer:
D. x=15.
6x +4x +12 +18= 180
10x +30=180
10x=150
x=15
Plug in 15 back into x to check:
6(15) +4(15) +12 +18= 180
150+30=180
180=180
Looks supplementary from picture (not entirely sure). Usually when angles are congruent they are marked with matching lines (2 angles either have 1, 2, or 3 lines to indicate this).
Step-by-step explanation:
If they're congruent, they're equal angles. You would set them equal to each other then solve. If they're supplementary, the angles do not equal each other, but both add to 180 degrees--if supplementary, don't set equal, add both equations together, have 180 on the other side of equation, then solve.
