Respuesta :

Answer:

b = 16

Step-by-step explanation:

the sum of the 3 angles in a triangle = 180°

sum the angles and equate to 180

b + 15 + 8b - 18 + 39 = 180

9b + 36 = 180 ( subtract 36 from both sides )

9b = 144 ( divide both sides by 9 )

b = 16