Question 977923
This answer can be found without any algebra.  Since the number is two digits and the digits add to 15, 
the choices are 69, 78, 87, and 96.  Adding 9 to 96 gives 105 a 3 digit number.  Adding 9 to 87 gives 96, which isn't the reverse of 87. 
And 69 + 9 = 78. Again, not the reverse.
So the answer is 78.  78 + 9 = 87