A concave polygon has at least one "sunk in" place. That means it has an interior angle which has measure greater than 180o. It is indicated with the red arc.The sum of all measures of an n-sided polygon is given by the formula: A pentagon has 5 sides so n=5 So we add the angle measures and set that equal to 540o. m∠A + m∠B + m∠C + m∠D + m∠E = m∠D = 540o xo + (3x)o + (3x)o + xo + (7x)o = 540o (15x)o = 540o xo = 36o You can answer the questions from here. Edwin