sum of the digits of a 2 digit number is 11. the given number is les than the number by interchanging the digits by 9 . find the number

Answer 1

t + u = 11

10t +u = 10u +t -9 => 9t - 9u = -9

Multiply the first equation by 9 => 9t + 9u = 99

Add the 2 equations to eliminate the u and solve for t. The get the value for u using the value for t.