If m∠abc = 80°, what is m∠dbc? justify your reasoning.
using the angle addition postulate, 20 + m∠dbc = 80. so, m∠dbc = 60° using the subtraction property of equality.
using the angle addition postulate, 20 + 80 = m∠dbc. so, m∠dbc = 100° using the addition property of equality.
using the addition property of equality, 20 + 80 = 100, so m∠dbc = 100°.
using the subtraction property of equality, 80 − 20 = 60, so m∠dbc = 60°.