It is clear that the value of m∠ABC can be determined by adding m∠ABD and m∠DBC because m∠ABC the segment BD divides the angle m∠ABC into two adjacent angles m∠ABD and ∠DBC.
Therefore,
m∠ABC = m∠ABD + m∠DBC
= 61° + 59° ∵ m∠ABD = 61°, m ∠DBC = 59°
= 120°
Therefore, we conclude that the value of m∠ABC = 120°
