Step-by-step explanation:
a+b+c=78
b=10+a
c=2b
then, we back the first
a+10+a+2b=78
2a+2b=78- 10
2a+2(10+a)=68
2a+2a=48
4a=48
a=12
b=22
c=44
Answer:
73 degrees
supplementary means angles that add up to 180 degrees