The sum of a two-digit number and the number obtained by reversing its digits is 121.

 Find the number, if its unit place digit is 5.

Given, the Unit place digit is given as 5.
Let x be the tens place digit.
Number formed = 5 + 10x
Number obtained by reversing the digits = 5 × 10 + x 

                                                                         = 50 + x
As per the conditions, we have:
⇒ 5 + 10x + 50 + x = 121
⇒ 11x + 55 = 121
⇒ 11x = 121 – 55 (Transposing 55 to RHS)
⇒ 11x = 66
⇒ x = 6
Thus, the tens place digit = 6
Hence the required number = 5 + 6 × 10 = 5 + 60 = 65