So according to the nature of parallelogram:

∠ADC =∠B = 80； ∠ECD= 180-80= 100 .

The parallel line with point AB passing through E intersects with AD at F, connects BF and intersects with AE at 0.

Two parallelograms ABEF and FECD are obtained.

Because BE=CE,

The triangle CDE is an isosceles triangle with ECD = 180-80 = 100.

So EC=CD

So BE=CE=AB=CD,

So these two parallelograms are equal diamonds.

From the nature of the diamond, we can know that the diagonal of the diamond is vertically bisected.

So AO=3/2= 1.5,

So in AOF of RT triangle, AF=2.5, AO= 1.5.

So FO=√(AF? -Huh? )=√(2.5? - 1.5? )=2

So BF=4

So diamond ABEF=0.5*AE*BF=6.

So the area of parallelogram ABCD is 2*6= 12.

Summary: The main knowledge of this problem lies in mastering the properties of parallelogram and rhombus. There is also a clever use of the Pythagorean theorem of right triangle. This question is too simple for us now. In fact, junior high school mathematics is not difficult. You just started learning mathematics in the second day of junior high school. Thoroughly master book knowledge.

Let me tell you some experiences of studying science from junior high school to senior high school and then to university. I hope it will be helpful to your future study: according to the process and effect of my previous study of mathematics and physics (each subject has several full marks), I can draw the following experiences: I hope it will be helpful to you.

I think learning mathematics and physics should be from books to exercises; From easy to difficult; From simple to complex; From quality to quantity; From slow to fast. (that is, "five gradients")

First of all, from books to exercises, we should "thoroughly understand" books and understand and memorize the above knowledge. If you can't remember for a while, you can put it aside first (get familiar with the knowledge points by doing the questions), and then do some related questions according to the knowledge points.

When you do a problem, it's easy before it's difficult, that is to say, you should be careful not to blindly do too difficult problems first. Do some simple questions first, the purpose is to consolidate knowledge points and get familiar with them, and then gradually become more difficult questions. This has achieved the purpose of strengthening.

As for the simple to complex, that is to say, first do some topics that contain a single knowledge point, and then sum up the knowledge points of the topic, and then gradually strengthen the depth and do topics that contain multiple knowledge points.

From quality to quantity, that is to say, when we start, we should pay attention to quality, not quantity. Even if you can only do one question at the end of the day, as long as it is right and understood. We have also gained something; But if you do a lot of questions at the end of the day, they are all wrong, and you don't master any questions, it is useless. Only we can guarantee the quality and accuracy of the problem, and then slowly turn it into quantity.

As for from slow to fast, it is an auxiliary exercise for the exam. As we all know, time is very tight during the exam. Time is like money. Every minute is precious. At ordinary times, we should strengthen training, ensure accuracy while slowing down, and then slowly improve the speed in all aspects. Finally, it is fast and accurate at present.

As for other materials, books alone are definitely not enough. There must be information. At least two materials (more if there is enough time), a book with shallow knowledge points, and a topic that consolidates knowledge points; The other is a comprehensive training book. Finally, you can do a set of wrong questions and a set of questions. The wrong question set is used to classify the questions you did wrong, summarize the reasons for the mistakes and summarize the knowledge points. Do you know the knowledge points? When you have mastered it, mark the problem or delete it directly. As for the topic set, it is used to record classic and typical topics. Therefore, learning science can be summarized as "five books" (book, follow-up exercise, comprehensive exercise, wrong title book and final book. )

If we can achieve "five gradients" and "five books". I believe that it will no longer be a problem for you to learn math, science and health well.