Answer:
3500.
Step-by-step explanation:
We have been given that Cesar Chavez lead a March with 6,300 people. The ratio of marchers who were not farm-workers to farm-workers is 4:5. We are asked to find the number of marchers, who were farm-workers.
First of all, we will find the ratio of farm-workers to total marchers as:

To find the number of marchers, who were farm-workers, we need to find
of whole marchers.



Therefore, 3500 marchers were farmers.