The unknown angles when line BD bisect the angle ABC is as follows:\
How to find an angle when a line bisect an angle?
An angle bisector divides and angle into 2 equal angles.
Therefore, line BD bisect angle ABC.
Hence,
let's find m∠ABD
if m∠ABD = 6x + 4
m∠DBC = 8x - 4
Therefore,
m∠ABD = m∠DBC
6x + 4 = 8x - 4
6x - 8x = -4 - 4
-2x = -8
x = -8 / -2
x = 4
Therefore,
m∠ABD = 6x + 4 = 6(4) + 4 = 24 + 4 = 28°
let's find m∠ABC
If m∠ABD = 5y - 3
m∠DBC = 3y + 15
Hence,
m∠ABD = m∠DBC
5y - 3 = 3y + 15
5y - 3y = 15 + 3
2y = 18
y = 18 / 2
y = 9
Therefore,
m∠ABC = m∠ABD + m∠DBC
m∠ABC = 5(9) - 3 + 3(9) + 15
m∠ABC = 45 - 3 + 27 + 15
m∠ABC = 84°
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