Question 381751
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Hi,         
Let x and (7-x) represent the original ten and units digits respectively
Question states:
Reversing its digits increases the number by 9
[10x + (7-x)] + 9 = 10(7 -x) + x
Solving for x
  9x + 16  = 70 - 9x
  18x = 54
    x = 3, the original ten's dgit, the original one's digit is 4.   (7-3)

CHECKING our Answer
   34 + 9 = 43