It is a common belief
A "common belief" cannot be used as an alternate reference to "Some people believe". The reason? When you say "common" it indicates, by definition; an adjective that refers to a universal, widespread, or general knowledge. The "universal" aspect of the definition contradicts the "some" reference in the original. This incorrect word usage will negatively affect your LR score. Be careful of your word usage because incorrect meaning will change the way the thought is viewed and will pull down not only your LR, but also your C+C and GRA scores.
Your first paragraph is incomplete and will result in additional task deductions. While the prompt restatement was represented to the best of your writing ability, you neglected to present your personal opinion as necessary for the task. It clearly states that you must discuss your opinion. Therefore, it is a required part of the writer's opinion as a part of the thesis statement or reasoning basis for the discussion of your personal opinion.
The way the essay is written, the reasoning paragraphs must number a maximum of 3. That is, you must equally discuss the 2 public opinions prior to the presentation of your personal opinion. Your personal opinion must clearly be cohesive enough to connect to one of the 2 public opinions. The lack of the 2nd public opinion discussion and sudden jump to your personal opinion will result in this essay being scored as an incomplete discussion persentation.
This is not a bad start to the practice essays. However, you need to become more familiar with the 2 types of approaching this comparative discussion essay. Samples below should help you become clearer about how to develop this type of discussion prompt. Just click on Similar Discussions [+] to see similar presentations from previous exam takers.