В предложении должна быть сравнительная степень, плиз помогите

1 My room is not tidier than my sister`s 2 Sirius is the brightest star in the sky at night 3 This is not the most difficult question you have to answer. 4 Life now is easier than a hundred years ago 5 Is Moscow bigger than London? 6 I am the youngest person in my family. 7 Everest is the highest mountain in the world. 8 The weather today is much worse than it was a month ago.