Bar model method to solve this Math In Focus Workbook 5A (Chapter 4 Multiplying and Dividing Fractions and Mixed Numbers) question:
"Mimi's market sold 24 heads of lettuce one morning. That afternoon 2/7 of the remaining heads of lettuce were sold. The number of heads left was now 1/2 of the number the market had at the beginning of the day. How many heads of lettuce were there at the beginning of the day?"