A whole number is a number that we use in our common day conversations like, there are 8 apples inside the basket, you wouldn't say there are 8.25 apples in the basket because it would make no sense. Whole numbers are numbers that aren't decimals or any other form other than 0,1,2,3,etc. To round numbers up and down you also need to know that if a number is less than 4 then it will stay the same or decrease, if the number is 5 and up then it will increase.
79.531 rounded to the nearest whole number would be 80. Your answer is 80.