What's the answer help pls

Answer:
48°
Step-by-step explanation:
The m in front of the angle notation refers to the measure of the angle labeled A, B and C (with vertex at B)
Two Angles are Supplementary when they add up to 180 degrees.
HENCE,
∠A + ∠B =180 (given)
⇒4x - 16 +8x + 4 = 180°
⇒12x - 12 = 180°
⇒12x = 192
⇒x = 16 ----1
substituting eq1 in ∠A,
=> 4(16) -16
=> 64 - 16
=> ∠A = 48°
Answer:
48
Step-by-step explanation:
The definition of supplementary means that the two angles add up to 180. so you set both expressions up to where they add to 180. like this
4x-16+8x+4=180
combine like terms
12x-12=180
12x=192
divide to get x
x=16.
You need the measure of angle A so you plug it back in
4(16)-16
64-16
48 is the measure of angle A, and since these angles are supplementary, that means angle B is 132