Finding Percents with Proportions - Examples & Practice

The popcorn stands at the movies are keeping track of the flavors of popcorn sold. There are $3$ flavors offered: caramel chocolate chunk, kettle, and butter. In one night, $10$ boxes of caramel chocolate chunk were sold, $36$ boxes of kettle were sold, and $28$ boxes of butter were sold. What percentage of the boxes sold were kettle?