18. At the Summer Olympics in Barcelona,
Spain, Canadian Mark Tewksbury won the
100-m backstroke swimming competition in
53.98 s. Martin Lopez-Zubera of Spain won
the 200-m backstroke in 1 min 58.47 s. Who
swam faster and by how much?

If m∠abc = 70°, what is m∠abd? justify your reasoning.  using the addition property of equality, 40 + 70 = 110, so m∠abd = 110°.  using the subtraction property of equality, 70 − 30 = 40, so m∠abd = 30°.  using the angle addition postulate, 40 + m∠abd = 70. so, m∠abd = 30° using the subtraction property of equality.  using the angle addition postulate, 40 + 70 = m∠abd. so, m∠abd = 110° using the addition property of equality.