the difference between a 2-digit number and the number obtained by interchanging its digit is 63.what is the difference between the digits of the number.

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

Then the number is

10a+b

Now interchanging the digits the number becomes

10b+a

Now difference between the numbers are

10a+b-(10b+a) = 10a+b-10b-a = 9a-9b

Now factorising we get

9(a-b) = 63

a-b = 7

So the answer is 7.