Writing Feedback / IELTS ....Fast Food is becoming more popular? [8]

seems like u provide little info. try to use more transitional words to connect your sentences.

Writing Feedback / IELTS: Is it fair that sportmen earn far more money than doctors and teachers? [5]

Well, to my idea about your writing is that you should have a better introduction (the one you wrote sounds too simple). And in the body, you should add extra examples.