Simplify the following text for a Grade 13 native English-speaking person.
Original: Romans used whitewashed walls in their markets in which sellers , money lenders , and slave traders wrote their announcements and advertised for their products , and to attract the attention of customers they added attractive designs to their announcements .
Simplified: Romans used whitewashed walls in their markets in which sellers , money lenders , and slave traders wrote their announcements and advertised for their products , and to attract the attention of customers they added an attractive design .