The difference between a two digit number and the one obtained by reversing its digits is 54. If one of the digits is 2, what is the other?
Let the numbers be a and b. ab = 10a + b, and ba = 10b + a. The difference is 10a + b - (10b + a) = 9(a - b). It is given that 9(a - b) = 54, ⇒ a - b = $54/9$ = 6, ⇒ the difference between the digits is 6. If one of the digits is 2, the other can be 8.