Isolating the variable 'a' in the expression, we have:

So the correct option is B.
Answer:
x = 7
Explaination:
ABC = 40°
and BD bisects the angle so ABD = 20°
so 3x-1=20
solving for x gets us
x = 7
1/3, 0,1,-2.....neither geometric or arithmetic
Answer:
∠2 = 18°
Step-by-step explanation:
∠WXZ = ∠1 + ∠2 ← substitute ∠1 = 3∠2
∠WXZ = 3∠2 + ∠2, that is
72 = 4∠2 ( divide both sides by 4 )
18 = ∠2, that is
∠2 = 18°