Question

the difference between a two digital number and the number obtained by interchanging it's digital is 63 . what is the difference between the digits

Answer 1

xy - yx = 63

xy can be written as 10x + y and yx can be written as 10y + x

so substituting we get

10x + y - 10y -x = 63

9x - 9y = 63

x - y = 7