What is the area of a trapezoid abcd with bases ab and cd, if: ab = 10 cm, bc=da=13 cm, cd=20 cm?

What is the total surface area of this square pyramid?

Find the area of an equilateral triangle with a side of 6 inches

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.