A palindrome number is the same when read backwards, like 393 or 555.
"Find the largest palindrome number from the product of two 3-digit numbers."
I suggest two nested loops and a function "Is Palindrome" - the function should convert the number to string, to work out if the reverse is the same number.
The ranges for x and y go from 100 to 999 in this example -as we want to find out the result of multiplying 3 digit numbers. All candidates are appended to the list "retVal".