Question

the sum of the digits of a 2-digits number is 13 the number formed by interchanging the digits

Answer 1

so the number is 76
and number formed by interchanging it's digits we get 67 and their sum is 143
hope it helps...

Answer 2

Let the tens digit be 'x'
then ones digit = (13 - x)
Number = 10x + (13-x)
= 10x + 13 - x
= 9x + 13
No. on interchanging digits
= 10(13 - x ) + x
= 130 - 10x + x
= 130 - 9x

Information is insufficient because there can be many no.s
satisfying the above given condition like
58 , 85 , 49 , 94 , 67 , 76 etc.