Answer: 1111
This is found through trial and error. A computer can be used to help search for the answer very quickly.
Here are all of the ways to form 1111 using two different 3-digit palindromes
- 202+909 = 1111
- 303+808 = 1111
- 404+707 = 1111
- 505+606 = 1111
If your teacher requires two different pairs of digits in the answer, then the answer would be 1221. There are a lot more ways to form 1221 (exactly 32 different sums). Here's a select set of examples.
- 232+989 = 1221
- 323+898 = 1221
- 363+858 = 1221
- 393+828 = 1221
- 424+797 = 1221
- 565+656 = 1221
There are 26 other ways to form a sum of 1221 when using two different 3-digit palindromes.
Side note: There isn't a way to form the sum 1001 using two different 3-digit palindromes.