During the lunch rush, the "catch of the day" is ordered 24 times. if the number of "catch of the day" orders represents 2/9 of the total lunch orders x, which equation could be used to determine the number of lunch orders taken that day?

This can be seen as a ratio of 2 numbers. It it says that 2/9 is the ratio of catchOfDay/totalLunches.
So:
2/9 = catchOfDay/totalLunches
It also says that the catchOfDay was ordered 24 times and we want to find totalLunches, represented by x.
So:
24/x = catchOfDay/totalLunches
Putting the 2 equations together we can conclude:
2/9 = catchOfDay/totalLunches = 24/x
simplifying would give a final answer of:
2/9 = 24/x

If we wanted to solve for x, we cross multiply to try and isolate the x and get:
2x = 24 * 9
divide both sides by 2:
x = 24 * 9 / 2
Working this out then we get:
x = 108