The lowest airport in the world is Atyrau Airport in Kazakhstan. Its
runway is 72 feet below sea level. A passenger in a small airplane on
the runway holds her phone exactly 4 feet above the runway. What
is the elevation of her phone? Use a negative sign where appropriate,
and don't include units when typing in the secret answer.
Your

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.