SOLUTION: If 36 is added to a certain double digit number, the result is the number with the digits reversed. The ones digit of the number is 1 more than twice the tens digit. What is the nu

Let the 10's digit be x
Then unit's digit is 2*x + 1
Number itself is 
Adding 36 to the number gives:  -- (1)
This is equal to the number with digits reversed i.e. one's digit is x and
10's digit is 2*x + 1
Value of the reversed number is  --(2)
Equating (1) and (2), since they both refer to the same number:


Simplifying:
 or 

So 10's digit is 3 and one's digit is 3*2 + 1 = 7.
The number is 
Adding 36 gives 73 which is the reversed number - correct!

Hope you got it :)