Be kind but firm is this statement sentence

What is the value of x when x + 7 = 21?

Worth 30 points! in this diagram, both polygons are regular. what is the value, in degrees, of the sum of the measures of angles abc and abd?

Match the following reasons with the statements given to create the proof. 1. do = ob, ao = oc sas 2. doc = aob given 3. triangle cod congruent to triangle aob vertical angles are equal. 4. 1 = 2, ab = dc if two sides = and ||, then a parallelogram. 5. ab||dc if alternate interior angles =, then lines parallel. 6. abcd is a parallelogram cpcte