Explain the relationship (or connection) between the volume formula for a cylinder and a cone?

On a architect's drawing of a house, 1 inche representa 1.5

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.

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?