Explanation:

Sol. Ans.(c). 

Each letter represents different digits.

Unknown digits are 6 (A, B, C, D, E, F). Each digit is greater than 3 (possible digits are 4, 5, 6, 7, 8, 9). So each of these digits (4-9) will be used. We have to find A – D (or D – A).

Here, C + F is ending with 2. So, C and take two values 8 or 7. If C is 8 then F is 4 and if C is 7 then F is 5. In any case B + 2 + 1 (carry) is ending with 0 so B = 7. It means C can’t take value 7, so C = 8 and F = 4.

Now F + 3 + 1 (carry) is ending with 9 so E = 5. Hence there is no carry forward in the next term i.e. A + D = 15 and remaining digits are 9 and 6. Thus 9+ 6 = 6 + 9 = 15.

So the difference between A and D is 3. So correct option is (c).