In last week's lesson I wrote the following sentence in my overview paragraph:
It is clear that the principal reason why Americans travelled in 2009 was to commute to and from work.
Moving on to the 'details' paragraphs, it's fine to repeat this point because we're now going to include the number or statistic. For example:
In 2009, 49% of the trips made by Americans.....
Can you finish the sentence above?