Calcular el área de esta figura

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?

We just started the introduction into circles and i have no idea how to do this.

An office supply company conducted a survey before marketing a new paper shredder designed for home use. in the survey, 80 % of the people who tried the shredder were satisfied with it. because of this high satisfaction rate, the company decided to market the new shredder. assume that 80 % of all people are satisfied with this shredder. during a certain month, 100 customers bought this shredder. find the probability that of these 100 customers, the number who are satisfied is 69 or fewer.