A recent survey determined that 7 out of 9 students eat school lunch at least once a week.if 450 were surveyed how many week?

If 7 out of 9 students eat school lunch at least once a week, that's a fraction of 7/9.

To find out how many of the 450 surveyed students eat school lunch at least once a week, we multiply the total number of students surveyed by the fraction:

450 * (7/9) = 350

So, $\boxed{350}$ students eat school lunch at least once a week.