Carbon-11 has half-life of 20 minutes. if a 50 gram sample of carbon -11 begins to decay, write a model for the amount, a, that is still radioactive after m-minutes. then, use your model to determine how much of the original sample is still radioactive after a half- hour. round to the nearest tenth of a gram

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.