Let x and (7-x) represent the original ten and units digits respectively
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
You can put this solution on YOUR website! Let the digits of the number be x and y.
So the number is xy (note: this does not mean x times y).
x+y=7 and yx=xy+9
In order for yx to equal xy+9, x=y-1.
Now we have the two equations x+y=7 and x=y-1.
x+y=7 -> x=7-y
Plug that into one of the original equations: x+4=7
The number is 34.