Need help for 18) 21) Solve each equation and check. Show all work please

Find the area of the regular hexagon if a side is 20 cm.

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.

Type the correct answer in each box. use numerals instead of words. if necessary, use / fir the fraction bar(s). the graph represents the piecewise function: h