To find the average number of square yards each person will mow, you can divide the total area of the lawn by the number of people mowing it.
The total area of the lawn is 600,000 square yards, and there are 12 people.
\[ \text{Average square yards per person} = \frac{\text{Total area}}{\text{Number of people}} = \frac{600,000 \text{ square yards}}{12} \]
Calculating that:
\[ \frac{600,000}{12} = 50,000 \]
So, the average number of square yards each person will mow is 50,000 square yards.