If the difference between a two-digit and the number obtained by reversing its digits is 27, then find the difference between the digits of the two-digit number.

Let the tens digit be $a$ and the units digit be $b$.

The two-digit number $= 10a + b$

The reversed number $= 10b + a$

$(10a + b) - (10b + a) = 27$

$9a - 9b = 27$

$9(a - b) = 27$

$a - b = 3$

The difference between the digits is $3$.