Write all possible 3-digit numbers using the digits 7, 0 and 6. Repetition of digits is not allowed. Also find their sum.

We are required to write 3-digit numbers using the digits 7, 0 and 6, where repetition of digits is not allowed.

The digit 0 cannot be put at hundred's place because that would make the number only 2-digit.

Keeping 0 at unit's place, 3-digit numbers are 760 and 670.

Keeping 0 at ten's place, 3-digit numbers are 706 and 607.

All possible 3-digit numbers: 706, 760, 607, 670.

Sum = 706 + 760 + 607 + 670

= 2,743

Hence, all possible 3-digit numbers are 706, 760, 607, 670 and their sum is 2,743.