The difference between the digits of a two-digit number is 4. What is the digit in the unit's place?

To find out the answer, which of the information given in the statements P and Q is/are sufficient:

P: The difference between the number and the number obtained by interchanging the positions of the digits is 36.

Q: The sum of the digits of that number is 12.

Only Q is sufficient

Here,

If we have sum of the digits of the number and also difference of the digits of the number, then we can find both the digits by adding and subtracting the equations.

Like, if we have,

a + b = x and a - b = y,

then we can find the values of a and b.

Therefore, only statement Q is sufficient for find the answer.