I ask people if they need help, especially if they don't have tools or know what to do. If asked, I will just say "I am good" should no help be needed. One day I had a flat and changed it in front of a college when a guy on a BMX rolled up and told me that I should use thorn resistant tubes. I told him that I was good with what I had and needed to get to work. He sat on his bike and stared at me for a few minutes which I thought was annoying yet he never offered help. Some people!