You have to order the following numbers from greatest to least
797.476
751.529
797.251
First order the values looking only at their integers. So first come the values with "797" and then the value with "751"
797.476
797.251
751.529
Now that you have the integers ordered you have to pay atention to the decimal values:
.476
.251
For this part you can order them using the same rules as when you order integers, meaning, 400 is greater than 200 so that value comes first:
797.476, 797.251, 751.529