For me it was number 7. I fought with it for a number of years. I went on summer break one year around 8 or 9, came back and all my 7's were backwards again. Th

For me it was number 7. I fought with it for a number of years. I went on summer break one year around 8 or 9, came back and all my 7's were backwards again. Thing is I couldn't see it till the teacher pointed it out.