- Somebody took my bag.
- I was happy to see somebody coming to help at last.
- I couldn’t answer the question because I knew nothing at all.
- There is nothing difficult here, it is easy.
- We helped mum to do something about the house.
В утвердительных предложениях обычно употребляются somebody и something; anything используется преимущественно в вопросах и отрицаниях, а nothing выражает отрицание.