Respuesta :

Answer:

∠ B = 99°

Step-by-step explanation:

Supplementary angle sum to 180°

Sum A and B and equate to 180

3x - 12 + 4x - 25 = 180 , that is

7x - 37 = 180 ( add 37 to both sides )

7x = 217 ( divide both sides by 7 )

x = 31

Then

∠ B = 4x - 25 = 4(31) - 25 = 124 - 25 = 99°