Question

the digits of a two digit number differ by 5 if the digits are interchanged and the resulting is added to the original number then we get 99 find the original number

Answer 1

let the digit be xy.
and required number be 10x + y.
x - y = 5 ------(1)
10x + y + 10y + x = 99
11x + 11y = 99
x + y = 9-----(2)
from 1 and 2
x = 7
y = 2
Hope this helps