07. KNOWING OUR NUMBERS
Explanation:
998000
We know that, the successor of a whole number is the number obtained by adding 1 to it and the predecessor of a whole number is one less than the given number.
So, the successor of 999 = 999 + 1 = 1000 and the predecessor of 999 = 999 - 1 = 998
Product of successor and predecessor of 999 = 1000 × 998 = 998000