Does anyone know how to do this ? what is the answer ?

Justifying my reasoning, using the angle addition postulate, 20 + m∠dbc = 80. so, m∠dbc = 60° using the subtraction property of equality. So, m∠dbc = 100° using the addition property of equality.

Step-by-step explanation:

a) using the angle addition postulate, 20 + m < dbc = 80. so, m < dbc = 60° using the subtraction property of equality.

b) using the angle addition postulate, 20 + 80 = m < dbc. so, m < dbc = 100° using the addition property of equality.

c) using the addition property of equality, 20 + 80 = 100, so m < dbc = 100°.

d) using the subtraction property of equality, 80 - 20 = 60, so m < dbc = 60°